Add compiler option for ignoring specific symbols

[uki-dev]

It is essential to have the ability to preserve certain symbols from renaming when pairing GLSLX with external frameworks in which specific symbols are static.

This is addressed by adding an additional variable ignoredSymbols List<string> to CompilerOptions which is checked against when renaming symbols & generating new symbol names.

Ignored symbols can be passed via the command line using the --ignored-symbols argument which accepts a JSON formatted array for example; --ignored-symbols='["foo", "bar"]'

[uki-dev]

@evanw pinging as unable to assign you as a reviewer.

[joscha]

@evanw any chance to get your eyes on this and some feedback on how to improve/change to get this merged, please?