[Bug bootstrap/61006] libcpp/lex.c: must use 'enum' tag to refer to type "raw_str_phase"

[spamcop at tgos dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61006

--- Comment #2 from spamcop at tgos dot net ---
Okay, but looking at the rest of the code, this seems to be the only
enum/struct/union that is not correctly "typed" according to C rules. E.g. all
the other variables of enum type have `enum` in the variable declaration and if
I just fix this one line, the file compiles as standard C without any problem.
So if nothing else than this line is a at least a serve break of style compared
to the rest of the file and as far as I can tell the only reason why this file
is not standard C and would need a C++ compiler.