Add support for GL_ARB_shading_language_include. Usage is identical to
the way GL_GOOGLE_include_directive currently works glslang (since
GL_ARB_shading_language_include is inherently a runtime feature and
glslang is an offline compiler).
Users can simulate their runtime environment by using a custom
glslang::TShader::Includer or using filenames that match their GL
runtime names.
Closes#249.
Any previous use would only be for "", which would probably mean changing
include(...) -> includeLocal(...)
See comments about includeLocal() being an additional search over
includeSystem(), not a superset search.
This also removed ForbidIncluder, as
- the message in ForbidIncluder was redundant: error results were
already returned to the caller, which then gives the error it
wants to
- there is a trivial default implementation that a subclass can
override any subset of (I still like abstract base classes though)
- trying to get less implementation out of the interface file anyway
This patch introduces a new extension, GL_GOOGLE_include_directive,
to enable support #include directives. It depends on the extension
GL_GOOGLE_cpp_style_line_directive.
