HLSL: Add location offsets per resource type

This PR adds the ability to offset sampler, texture, and UBO bindings
from provided base bindings, and to auto-number bindings that are not
provided with explicit register numbers. The mechanism works as
follows:

- Offsets may be given on the command line for all stages, or
  individually for one or more single stages, in which case the
  offset will be auto-selected according to the stage being
  compiled. There is also an API to set them. The new command line
  options are --shift-sampler-binding, --shift-texture-binding, and
  --shift-UBO-binding.

- Uniforms which are not given explicit bindings in the source code
  are auto-numbered if and only if they are in live code as
  determined by the algorithm used to build the reflection
  database, and the --auto-map-bindings option is given. This auto-numbering
  avoids using any binding slots which were explicitly provided in
  the code, whether or not that explicit use was live. E.g, "uniform
  Texture1D foo : register(t3);" with --shift-texture-binding 10 will
  reserve binding 13, whether or not foo is used in live code.

- Shorter synonyms for the command line options are available.  See
  the --help output.

The testing infrastructure is slightly extended to allow use of the
binding offset API, and two new tests spv.register.(no)autoassign.frag are
added for comparing the resulting SPIR-V.

glslang/Public/ShaderLang.h

@@ -300,6 +300,10 @@ public:
         const char* const* s, const int* l, const char* const* names, int n);
     void setPreamble(const char* s) { preamble = s; }
     void setEntryPoint(const char* entryPoint);
+    void setShiftSamplerBinding(unsigned int base);
+    void setShiftTextureBinding(unsigned int base);
+    void setShiftUboBinding(unsigned int base);
+    void setAutoMapBindings(bool map);
 
     // Interface to #include handlers.
     //
@@ -433,6 +437,7 @@ private:
 };
 
 class TReflection;
+class TIoMapper;
 
 // Make one TProgram per set of shaders that will get linked together.  Add all 
 // the shaders that are to be linked together.  After calling shader.parse()
@@ -470,6 +475,9 @@ public:
     int getAttributeType(int index);                 // can be used for glGetActiveAttrib()
     void dumpReflection();
 
+    // I/O mapping: apply base offsets and map live unbound variables
+    bool mapIO();
+
 protected:
     bool linkStage(EShLanguage, EShMessages);
 
@@ -479,6 +487,7 @@ protected:
     bool newedIntermediate[EShLangCount];      // track which intermediate were "new" versus reusing a singleton unit in a stage
     TInfoSink* infoSink;
     TReflection* reflection;
+    TIoMapper* ioMapper;
     bool linked;
 
 private: