Correct some slightly incorrect regular expressions:
* lisp/progmodes/cc-awk.el (c-awk-harmless-char-re) (c-awk-harmless-line-char-re, c-awk-_-harmless-nonws-char-re): [...\\\\...] -> [...\\...]. * lisp/progmodes/cc-engine.el (c-literal-limits): "*/" -> "\\*/". * lisp/progmodes/cc-mode.el (c-after-change-re-mark-unbalanced-strings): "\\\r" -> "\r".