Compile will fail on Unix, don't use backslash in includefiles

Rule "incslash" will raise this warning when it finds an include directive with backslashes. For example:

   {subdirectory\includefile.i}

The reason for this warning is that this sourcefile will not compile on Unix. Change the backslash into a forward slash so the source can be compiled on Unix and on Windows.

Compiled r-code used to be platform indepedent: you could develop on Windows, compile on Windows and simply FTP the r-code to Unix and it would just run fine (even though Progress did not actually guarantee that).
But this breaks if you develop on 32-bit Windows and deploy to 64-bit Unix: you just have to compile on the target platform to get working r-code. This rule helps to locate include directives that won't compile on Unix in your new and existing code.