Add antialias support for CanvasItem draw primitives

including
- rect, circle; both filled and unfilled.
- polyline, multiline

doc/classes/CanvasItem.xml

@@ -84,6 +84,7 @@
 				Draws a circle. See also [method draw_arc], [method draw_polyline], and [method draw_polygon].
 				If [param filled] is [code]true[/code], the circle will be filled with the [param color] specified. If [param filled] is [code]false[/code], the circle will be drawn as a stroke with the [param color] and [param width] specified.
 				If [param width] is negative, then two-point primitives will be drawn instead of a four-point ones. This means that when the CanvasItem is scaled, the lines will remain thin. If this behavior is not desired, then pass a positive [param width] like [code]1.0[/code].
+				If [param antialiased] is [code]true[/code], half transparent "feathers" will be attached to the boundary, making outlines smooth.
 				[b]Note:[/b] [param width] is only effective if [param filled] is [code]false[/code].
 			</description>
 		</method>
@@ -105,9 +106,12 @@
 			<param index="3" name="width" type="float" default="-1.0" />
 			<param index="4" name="dash" type="float" default="2.0" />
 			<param index="5" name="aligned" type="bool" default="true" />
+			<param index="6" name="antialiased" type="bool" default="false" />
 			<description>
 				Draws a dashed line from a 2D point to another, with a given color and width. See also [method draw_multiline] and [method draw_polyline].
 				If [param width] is negative, then a two-point primitives will be drawn instead of a four-point ones. This means that when the CanvasItem is scaled, the line parts will remain thin. If this behavior is not desired, then pass a positive [param width] like [code]1.0[/code].
+				If [param antialiased] is [code]true[/code], half transparent "feathers" will be attached to the boundary, making outlines smooth.
+				[b]Note:[/b] [param antialiased] is only effective if [param width] is greater than [code]0.0[/code].
 			</description>
 		</method>
 		<method name="draw_end_animation">
@@ -175,9 +179,11 @@
 			<param index="0" name="points" type="PackedVector2Array" />
 			<param index="1" name="color" type="Color" />
 			<param index="2" name="width" type="float" default="-1.0" />
+			<param index="3" name="antialiased" type="bool" default="false" />
 			<description>
 				Draws multiple disconnected lines with a uniform [param width] and [param color]. Each line is defined by two consecutive points from [param points] array, i.e. i-th segment consists of [code]points[2 * i][/code], [code]points[2 * i + 1][/code] endpoints. When drawing large amounts of lines, this is faster than using individual [method draw_line] calls. To draw interconnected lines, use [method draw_polyline] instead.
 				If [param width] is negative, then two-point primitives will be drawn instead of a four-point ones. This means that when the CanvasItem is scaled, the lines will remain thin. If this behavior is not desired, then pass a positive [param width] like [code]1.0[/code].
+				[b]Note:[/b] [param antialiased] is only effective if [param width] is greater than [code]0.0[/code].
 			</description>
 		</method>
 		<method name="draw_multiline_colors">
@@ -185,9 +191,11 @@
 			<param index="0" name="points" type="PackedVector2Array" />
 			<param index="1" name="colors" type="PackedColorArray" />
 			<param index="2" name="width" type="float" default="-1.0" />
+			<param index="3" name="antialiased" type="bool" default="false" />
 			<description>
 				Draws multiple disconnected lines with a uniform [param width] and segment-by-segment coloring. Each segment is defined by two consecutive points from [param points] array and a corresponding color from [param colors] array, i.e. i-th segment consists of [code]points[2 * i][/code], [code]points[2 * i + 1][/code] endpoints and has [code]colors[i][/code] color. When drawing large amounts of lines, this is faster than using individual [method draw_line] calls. To draw interconnected lines, use [method draw_polyline_colors] instead.
 				If [param width] is negative, then two-point primitives will be drawn instead of a four-point ones. This means that when the CanvasItem is scaled, the lines will remain thin. If this behavior is not desired, then pass a positive [param width] like [code]1.0[/code].
+				[b]Note:[/b] [param antialiased] is only effective if [param width] is greater than [code]0.0[/code].
 			</description>
 		</method>
 		<method name="draw_multiline_string" qualifiers="const">
@@ -283,9 +291,11 @@
 			<param index="1" name="color" type="Color" />
 			<param index="2" name="filled" type="bool" default="true" />
 			<param index="3" name="width" type="float" default="-1.0" />
+			<param index="4" name="antialiased" type="bool" default="false" />
 			<description>
 				Draws a rectangle. If [param filled] is [code]true[/code], the rectangle will be filled with the [param color] specified. If [param filled] is [code]false[/code], the rectangle will be drawn as a stroke with the [param color] and [param width] specified. See also [method draw_texture_rect].
 				If [param width] is negative, then two-point primitives will be drawn instead of a four-point ones. This means that when the CanvasItem is scaled, the lines will remain thin. If this behavior is not desired, then pass a positive [param width] like [code]1.0[/code].
+				If [param antialiased] is [code]true[/code], half transparent "feathers" will be attached to the boundary, making outlines smooth.
 				[b]Note:[/b] [param width] is only effective if [param filled] is [code]false[/code].
 				[b]Note:[/b] Unfilled rectangles drawn with a negative [param width] may not display perfectly. For example, corners may be missing or brighter due to overlapping lines (for a translucent [param color]).
 			</description>