HLSL: phase 3a: Add sub-vec4 rwtexture formats (qualifier.layoutFormat)

This PR sets the TQualifier layoutFormat according to the HLSL image type.
For instance:

  RWTexture1D <float2> g_tTex1df2;

becomes ElfRg32f.  Similar on Buffers, e.g, Buffer<float4> mybuffer;

The return type for image and buffer loads is now taken from the storage format.
Also, the qualifier for the return type is now (properly) a temp, not a global.

Test/hlsl.load.buffer.float.dx10.frag

@@ -0,0 +1,38 @@
+uniform Buffer <float> g_tTexbfs_test : register(t0);
+
+Buffer <float> g_tTexbfs;
+Buffer <int>   g_tTexbis;
+Buffer <uint>  g_tTexbus;
+
+struct PS_OUTPUT
+{
+    float4 Color : SV_Target0;
+    float  Depth : SV_Depth;
+};
+
+uniform int   c1;
+uniform int2  c2;
+uniform int3  c3;
+uniform int4  c4;
+
+uniform int   o1;
+uniform int2  o2;
+uniform int3  o3;
+uniform int4  o4;
+
+PS_OUTPUT main()
+{
+   PS_OUTPUT psout;
+
+   // Buffer
+   float r00 = g_tTexbfs.Load(c1);
+   int   r01 = g_tTexbis.Load(c1);
+   uint  r02 = g_tTexbus.Load(c1);
+
+   // TODO: other types that can be put in sampler buffers, like float2x2, and float3.
+
+   psout.Color = 1.0;
+   psout.Depth = 1.0;
+
+   return psout;
+}