Updated command-line options, adding -o for saving binaries, -G for OpenGL SPIR-V validation, -v etc.

Old uses should still work as they did before.
Also encapsulated use of these flags during parsing, for the parse context.
Added SPIR-V version to -v.

SPIRV/GlslangToSpv.h

@@ -36,6 +36,7 @@
 
 namespace glslang {
 
+void GetSpirvVersion(std::string&);
 void GlslangToSpv(const glslang::TIntermediate& intermediate, std::vector<unsigned int>& spirv);
 void OutputSpv(const std::vector<unsigned int>& spirv, const char* baseName);