R-devel 2017-02-15: repeated line in /src/gnuwin32/MkRules.dist

Hello.

Unless I am mistakedn, it seems that lines 49 and 72 are copies of
each other and only one should be necessary to set the whether or not
Windows is 32- or 64-bit. If it were my guess, I'd say lines 48 & 49
are redundant.

Thanks,

Avi