Mark all internal parse_ methods as static

[Morriar]

From all the methods only called from inside parse.c, some methods where marked as static some other not.

Let's standardize all of them as static unless exposed in the parse.h file.

[soutaro]

🙏

[ParadoxV5]

IIRC, marking internals as static removes them from the shared library’s function table. This is beneficial in binary size reductions if the header implies that they’re not meant to be exposed.