RunProcess arguments should be pre-processed using AbsoluteFileName

[szhorvat]

RunProcess's argument should be pre-processed with AbsoluteFileName.

Do this in the runProcess function.

User complaint: / separators don't work on Windows. ~ also does not work on Mac.

[szhorvat]

I decided not to fix this:

• In recent versions (11.2+?) RunProcess handles / as a path separator just fine on Windows
• / is not correct path separator on Windows anyway, and users can fix this on their end very easily (use the correct path separator)
• In some older versions of Mathematica, RunProcess misbehaves on non-English versions of Windows when paths contain non-ASCII characters. The typical workaround is to set an explicit working directory which may have a short 8.3 path name. AbsoluteFileName would change the short path name to a long one, bringing back the problems.

The best compromise is to leave things as they are.

Eventually all these problems will go away as people stop using old Mathematica versions.