PATCH: remove a CPP warning within comment

[John Marshall]

Sylvain Pion wrote:
>  /* ... \  
>   ... */
[...]
>        * cpplex.c (skip_escaped_newlines): Don't warn for spaces between
>        backslash and newline, when inside a comment.

Certainly it's worth suppressing the warning for C comments, but it's not
obvious that it shouldn't warn in C++ comments:

	// Lots of spaces after the backslash: \     
	foo ();  // Hey!  foo never got called!

    John