* etags.c (lowcase): Use the standard tolower function.

* etags.c (lowcase): Use the standard tolower function.
	(substitute): Remove some wrong and some useless code related with
	escape `\` character in regexp replacement string.
	(TEX_defenv): Added part, appendix, entry, index.  Removed typeout.
	(lang_suffixes): New suffixes: .hpp for C++; .f90 for Fortran;
	.bib, .ltx, .TeX for TeX (.bbl, .dtx removed); .ml for Lisp;
	.prolog for prolog (.pl removed).
	(massage_name, etags_getcwd): Use lowcase instead of tolower.
	(regex.h): Don't include it if REGEX_IN_LIBC is defined.
	(C_entries, find_entries): Added comments about memory leakage.
	(add_node): Dead code removed.