Bill Fisher: This patch fixes a bug where the regex parser doesn't advance the pointer after reading the third character of an octal escape (in awk mode).

That is, regex{"\141", awk} results in the regular expression /a1/ instead of just /a/.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@185449 91177308-0d34-0410-b5e6-96231b3b80d8