x86/Intel: address quoted-symbol related FIXMEs

x86/Intel: address quoted-symbol related FIXMEs

If in a "word ptr <address>" or alike construct the "ptr" part is
double-quoted, it shouldn't be recognized as the specific keyword we're
looking for (just like we don't recognize double-quoted operator or
register names anymore). Be careful though to tell closing from opening
double-quotes, as a quoted symbol may follow right afterwards.