Uniformity added to environment variable use for Windows build.

Two ways of using environment variable to build on windows were
proposed (one in dev, one in prod), now either one of them can be used.
Uniformity added to environment variable use for Windows build.

Two ways of using environment variable to build on windows were
proposed (one in dev, one in prod), now either one of them can be used.
Merge branch 'master' of ssh://gh/Frederic-bioinfo/rTANDEM

Conflicts:
	src/Makevars.win