Bump version to 10.4.0.0a3 and update Changes

Author: johnhaddon

Changes

@@ -1,4 +1,4 @@
-10.4.0.0ax (relative to 10.4.0.0a2)
+10.4.0.0a3 (relative to 10.4.0.0a2)
 ==========
 
 > Note : Changes marked with "(RB-10.3)" don't need to be mentioned in the release notes for the final release version of `10.4.0.0`. They are all inherited from `RB-10.3`.
@@ -10,6 +10,7 @@ Improvements
   - Added basic support for loading UsdLux lights (#1256).
   - Registered .usdz file format (RB-10.3).
   - USDScene : Added support for the `doubleSided` attribute (RB-10.3).
+- IECoreGL::Shader : Added support for integer sampler parameters (#1261).
 
 10.4.0.0a2 (relative to 10.4.0.0a1)
 ==========

SConstruct

@@ -58,7 +58,7 @@ ieCoreMilestoneVersion = 10 # for announcing major milestones - may contain all
 ieCoreMajorVersion = 4 # backwards-incompatible changes
 ieCoreMinorVersion = 0 # new backwards-compatible features
 ieCorePatchVersion = 0 # bug fixes
-ieCoreVersionSuffix = "a2" # used for alpha/beta releases. Example: "a1", "b2", etc.
+ieCoreVersionSuffix = "a3" # used for alpha/beta releases. Example: "a1", "b2", etc.
 
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