# operator drops the space that a comment stands for #718

In translation phase 3 each comment is replaced by one space character (C §5.1.1.2, C++ [lex.phases]). When an argument is stringified with #, each group of whitespace between tokens becomes one space (C §6.10.3.2), so a comment
between two tokens must give a space in the string.

#define str(x) #x
str(a/**/b)

gcc and clang output "a b". simplecpp outputs "ab".

When comments are kept in the output (like gcc -C), gcc keeps the comment in the string: "a/**/b". simplecpp already does the same, and that should not change.