remove unused tm_ucs2_str_length
clean up ucs2_str_codeat (née charat)
move char_encode to ucs2 suite (inverse of str_codeat)
reorganize "final" string handling functions to better clarify that some are for "internal colony string" (was called ucs2) and a few are for special UTF-8 stuff
travisplexer: pr-137-arm travis ci test