Expanding empty strings is valid but pointless;
macro args already skipped doing so, now other
`beginExpansion` calls do too.
This also fixes failed interpolations (which were
already non-fatal) to continue reading characters,
not evaluate to their initial '{' character.
Fixes#669Closes#368Closes#624
Deprecate PRINTT, PRINTV, PRINTI, and PRINTF
Default STRFMT("%f") to 5 fractional digits like "{f:}"
Any use of string formatting will share this default
This should significantly improve performance: on pokecrystal builds, perf
reported as much CPU time spent on `yyparse` as on `sym_UseNewMacroArgs`
Measurements show ~6 seconds of improvement on that codebase.
This also fixes#321, as a bonus, due to saner management!
