Accept free-form function names

[jvprat]

The function name parsing in "argscheck" is a bit restrictive, only allowing valid Lua identifiers. Since it's only used to show error messages I'd like to use more descriptive names, like "t[2]" or "local f1 inside f2".

I'm really bad with pattern matching, so I open it as a feature request ;)

[gvvaughan]

That seems reasonable... although it conflicts slightly with one of my goals to use the debug API to find the name of the symbol that was used to call the failing function. The problem there, of course, is that differing tail call elimination between Lua hosts makes figuring out where exactly to look less than straight forward; LuaJIT in particular sometimes loses track entirely (it's own error messages often don't list a symbol, presumably because that got optimized away by the JIT compiler in those cases).

I'll take a look at generalizing the parse pattern this weekend.