@ekextr using Scintilla word lists for that is unrealistic in the current state of things, it's way too slow. I tried populating the list of C preprocessor symbols in a plugin, with all the macros definitions, and it caused very annoying slowdowns. Nothing causing a lockup, but way enough to be noticeable and annoying. So I'd think that the very same kind of problem would show with a very large list of function names. Possibly worse as there are a lot more identifiers to check against. Or possibly less because there's nothing to further compute. Anyway, I think before searching down this path testing how Scintilla can cope with a *huge* keyword list is needed.
Also, as there is actual syntax for function declarations and call, it might make more sense to highlight that syntax rather than known function names.