Handle C++ raw strings.

Handle C++ raw strings.

* lisp/progmodes/cc-engine.el (c-raw-string-pos, c-depropertize-raw-string)
(c-depropertize-raw-strings-in-region,
c-before-change-check-raw-strings)
(c-propertize-raw-string-opener, c-after-change-re-mark-raw-strings): New
functions.

* lisp/progmodes/cc-fonts.el (c-basic-matchers-before): Insert a clause for
c-font-lock-raw-strings.
(c-font-lock-raw-strings): New function.

* lisp/progmodes/cc-langs.el (c-get-state-before-change-functions): Insert
c-before-change-check-raw-strings into the C++ value, and c-depropertize-CPP
into the values for C, C++, and Objective C.
(c-before-font-lock-functions): Insert c-after-change-re-mark-raw-strings into
the C++ value.

* lisp/progmodes/cc-mode.el (c-old-BEG, c-old-END): New variables.
(c-depropertize-CPP): New function, extracted from
c-neutralize-syntax-in-and-mark-CPP.
(c-neutralize-syntax-in-and-mark-CPP): Remove the call to
c-clear-char-property-with-value for 'syntax-table value '(1) at the beginning
of the function.
(c-after-change): Set c-old-BEG and c-old-END to the current values of
c-new-BEG and c-new-END.