[Bug preprocessor/8270] [6/7/8 Regression] back-slash white space newline with comments, no warning

[doug at cs dot dartmouth.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=8270

--- Comment #61 from doug mcilroy <doug at cs dot dartmouth.edu> ---
Contrary to comment #57, the GCC convention does affect the interpretation of
C-style comments. GCC rejects this Christmas tree with trailing spaces.

/*
  /\    
 /**\   
/****\  
*/