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/llrender/llglslshader.cpp

@@ -933,6 +933,23 @@ void LLGLSLShader::uniformMatrix3fv(U32 index, U32 count, GLboolean transpose, c
 	}
 }
 
+void LLGLSLShader::uniformMatrix3x4fv(U32 index, U32 count, GLboolean transpose, const GLfloat *v)
+{
+	if (mProgramObject > 0)
+	{	
+		if (mUniform.size() <= index)
+		{
+			UNIFORM_ERRS << "Uniform index out of bounds." << LL_ENDL;
+			return;
+		}
+
+		if (mUniform[index] >= 0)
+		{
+			glUniformMatrix3x4fvARB(mUniform[index], count, transpose, v);
+		}
+	}
+}
+
 void LLGLSLShader::uniformMatrix4fv(U32 index, U32 count, GLboolean transpose, const GLfloat *v)
 {
 	if (mProgramObject > 0)