In hindsight my emscripten-ifdef (70d416a8f63f) is nonsense.
As fpcrtl_glShaderSource() would not be defined and lead to compiling issues.
So either it's 3 ifdefs (in pas2cRedo, pas2cSystem and misc.c),
in order to toggle between fpcrtl_ and the native function,
or alternatively have no ifdef for it at all.
I'm going with none at all,
which means emscripten will compile with the original (const) function prototype,
being wrapped by the fpcrtl_ function, same as non-emscripten builds.