Skinned shaders were exceeding maximum amount of vertex uniforms on amd hardware.

-Changed the transform matrix uniform to a 3x4 matrix and packed translation into it to free up uniforms. (3x3 is converted to 3x4 internally, so we were needlessly eating 3*52 extra uniform slots. translationPalette might also have been treated as a vec4 internally too, wasting 52 more slots.)
-matrix3x4 requires opengl2.1 and newer, so added a new featuretable mask.
-Also added a featuretable mask to disable hardware skinning and deferred shading on hardware with less than 1024 vertex uniforms.
NOTE: On old old old amd hardware, evidently a 3x4 matrix might be upgraded to 4x4. I'm unsure, but I doubt such hardware has 1024+ uniform components available to begin with. 4x3 supposedly doesn't do this, but opengl is column-major, so this makes little sense.

indra/newview/featuretable.txt

@@ -301,6 +301,10 @@ RenderObjectBump			0	0
 list OpenGLPre15
 RenderVBOEnable				1	0
 
+list OpenGLPre21
+RenderAvatarVP				0	0
+RenderAvatarCloth			0	0
+
 list OpenGLPre30
 RenderDeferred				0	0
 RenderMaxTextureIndex		1	1
@@ -486,6 +490,7 @@ Disregard128DefaultDrawDistance	1	0
 list ATIOldDriver
 RenderAvatarVP				0	0
 RenderAvatarCloth			0	0
+RenderDeferred				0	0
 
 // ATI cards generally perform better when not using VBOs for streaming data
 
@@ -596,3 +601,7 @@ RenderShaderLightingMaxLevel	1	2
 list NVIDIA_GeForce_Go_7900
 RenderShaderLightingMaxLevel	1	2
 
+list VertexUniformsLT1024
+RenderAvatarVP					0	0
+RenderAvatarCloth				0	0
+RenderDeferred					0	0