[Bug c/33167] Hex constant characters with \x escape not parsing correctly

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=33167

--- Comment #5 from joseph at codesourcery dot com <joseph at codesourcery dot 
com> ---
The standard syntax production for octal-escape-sequence (C11 6.4.4.4#1) 
only allows one, two or three digits.