[phobos] linux.mak + osx.mak = GNUMakefile

[Andrei Alexandrescu]

Hey folks,


I was building Phobos on OSX when I ran into a makefile bug that I'd 
fixed in linux.mak. It was still present in osx.mak. I noticed the files 
are virtually identical, so why not merge them?

Since the one thing that linux.mak and osx.mak have in common is the 
fact that they're understood by gnu make (as opposed to win32.mak which 
is used by Walter's own make utility), I'm thinking the new makefile 
should be called GNUMakefile. That name is actually understood by gmake 
which means no more -f.

I'm operating this change and will check in soon, please let me know if 
you foresee any issues.



Andrei