#1719 CPP lexer #undef not processed

[Andrea Partinico]

example code:

#define T1
#undef T1

#if defined T1
   #warning "defined"
   #define TEST() printf("defined")
#else
   #warning "not defined"
   #define TEST() printf("not defined")
#endif

int main()
{
   TEST();
   return 0;
}

[Neil Hodgson]

Fixed by [eae289].