Limit visibility of symbols for internal libraries

Also remove `SPIRV/doc.cpp` from the `SPVRemapper` target as this
is part of `SPIRV`, causing ODR violations. Instead have
`SPVRemapper` link against `SPIRV`.

Fixes ODR violations.

OGLCompilersDLL/CMakeLists.txt

@@ -36,6 +36,7 @@ set(SOURCES InitializeDll.cpp InitializeDll.h)
 add_library(OGLCompiler STATIC ${SOURCES})
 set_property(TARGET OGLCompiler PROPERTY FOLDER glslang)
 set_property(TARGET OGLCompiler PROPERTY POSITION_INDEPENDENT_CODE ON)
+glslang_default_to_hidden_visibility(OGLCompiler)
 
 if(WIN32)
     source_group("Source" FILES ${SOURCES})