gfortran on cygwin needs make distclean to update correctly

[Tim Prince]

As stated in the subject, although gcc is rebuilt as required by any
updated functions (including config/i386/i386.c), gfortran is not, even
after a make clean.  I suppose this is some kind of cygwin/windows
related glitch.
I noticed this while attempting to verify optimization of the .p2align
parameters, having noticed that the 4,,10 setting for most Intel CPUs
can be improved upon occasionally by advancing to 4,,12, and that some
of the newer targets are set to 4,,15 which would have the effect of
unconditional 16-byte alignment.
Other gfortran improvements were observed, apparently due to trunk
updates since my last clean build.
In a few cases, gfortran doesn't apply .p2align while gcc does for an
exact functional translation, yet gfortran benefits more consistently
from max-unroll-times=4.  Effectiveness of increased unrolling seems to
depend on better alignment as well as code optimization.  I suppose loop
stream detector effective buffer size may be maximized by alignment.

-- 
Tim Prince