Flatten uniform arrays

This checkin adds a --flatten-uniform-arrays option which can break
uniform arrays of samplers, textures, or UBOs up into individual
scalars named (e.g) myarray[0], myarray[1], etc.  These appear as
individual linkage objects.

Code notes:

- shouldFlatten internally calls shouldFlattenIO, and shouldFlattenUniform,
  but is the only flattening query directly called.

- flattenVariable will handle structs or arrays (but not yet arrayed structs;
  this is tested an an error is generated).

- There's some error checking around unhandled situations.  E.g, flattening
  uniform arrays with initializer lists is not implemented.

- This piggybacks on as much of the existing mechanism for struct flattening
  as it can.  E.g, it uses the same flattenMap, and the same
  flattenAccess() method.

- handleAssign() has been generalized to cope with either structs or arrays.

- Extended test infrastructure to test flattening ability.

glslang/MachineIndependent/localintermediate.h

@@ -145,7 +145,8 @@ public:
         shiftSamplerBinding(0),
         shiftTextureBinding(0),
         shiftUboBinding(0),
-        autoMapBindings(false)
+        autoMapBindings(false),
+        flattenUniformArrays(false)
     {
         localSize[0] = 1;
         localSize[1] = 1;
@@ -176,6 +177,8 @@ public:
     unsigned int getShiftUboBinding()     const { return shiftUboBinding; }
     void setAutoMapBindings(bool map)               { autoMapBindings = map; }
     bool getAutoMapBindings()             const { return autoMapBindings; }
+    void setFlattenUniformArrays(bool flatten)      { flattenUniformArrays = flatten; }
+    bool getFlattenUniformArrays()        const { return flattenUniformArrays; }
 
     void setVersion(int v) { version = v; }
     int getVersion() const { return version; }
@@ -385,6 +388,7 @@ protected:
     unsigned int shiftTextureBinding;
     unsigned int shiftUboBinding;
     bool autoMapBindings;
+    bool flattenUniformArrays;
 
     EProfile profile;
     int version;