(regcomp): Append "__restrict" modifier to avoid warnings of some compilers. (build_collating_symbol): Change the type of characters from "unsigned char"
to "char", and append a cast to "char*" pointer in array subscript. (build_collating_symbol): Likewise. (build_equiv_class): Likewise. (build_charclass): Likewise. (re_compile_pattern): Remove incorrect cast. (re_compile_fastmap_iter): Change the type of characters from "unsigned char"
to "char", and append a cast to "char*" pointer in array subscript. (parse_bracket_exp): Likewise.