(PARAMS): Remove. All uses removed.

(PARAMS): Remove.  All uses removed.
All uses of _RE_ARGS removed, too.
Include <stddef.h>, <stdlib.h>, <string.h>, <limits.h>
unconditionally.
(bzero): Assume memset exists.
(memcmp, memcpy, NULL): Remove.
(SIGN_EXTEND_CHAR): Remove; all uses replaced by casts to signed
char, or assignments to local vars of type signed char.
(init_syntax_once, PREFIX(extract_number_and_incr),
PREFIX(print_partial_compiled_pattern),
PREFIX(print_compiled_pattern), PREFIX(print_double_string),
convert_mbs_to_wcs, print_fastmap, re_set_syntax,
PREFIX(regex_grow_registers), PREFIX(regex_compile),
PREFIX(store_op1), PREFIX(store_op2), PREFIX(insert_op1),
PREFIX(insert_op2), PREFIX(at_begline_loc_p),
PREFIX(at_endline_loc_p), group_in_compile_stack, insert_space,
wcs_compile_range, byte_compile_range, truncate_wchar,
PREFIX(re_compile_fastmap), re_compile_fastmap, re_set_registers,
re_search, re_search_2, PREFIX(re_search_2), re_match, re_match_2,
count_mbs_length, wcs_re_match_2_internal,
byte_re_match_2_internal, PREFIX(group_match_null_string_p),
PREFIX(alt_match_null_string_p),
PREFIX(common_op_match_null_string_p), PREFIX(bcmp_translate),
re_compile_pattern, re_comp, re_exec, regcomp, regexec, regerror,
regfree, PREFIX(extract_number)): Define with prototype.  Remove
now-unnecessary declaration, if any.
(byte_compile_range, PREFIX(regex_compile), re_comp, re_exec,
regcomp, regexec):
Remove now-unnecessary casts among pointer types.