regex: diagnose too-large repeat counts in EREs Previously, the code did not diagnose the too-large repeat count in EREs like 'b{1000000000}'; instead, it silently treated the ERE as if it were 'b\{1000000000}', which is unexpected. * lib/regcomp.c (parse_dup_op): Fail with REG_ESIZE if a repeat count is too large. REG_ESIZE is used nowhere else, and the diagnostic is a reasonable one for this problem. Another option would be to create a new REG_OVERFLOW error for repeat counts that are too large. (fetch_number): Return RE_DUP_MAX + 1, not REG_ERROR, if the repeat count is too large, so that the caller can distinguish the two cases. * lib/regex.h (_REG_ESIZE): Document that this is now a generic "Too large" return code, and that repeat counts are one example of this.