Update to host installation notes for GCC on Win2K

[Jeff Russell]

A suggested addition to the installation notes for:

Microsoft Windows (32 bit) enivoronment with Cygwin.

During the configuration step, use path names rooted at "/cygdrive" instead
of a drive lettter like "c:", as the colon confuses sed.

------
My build was sucessful:
$ ./config.guess
i686-pc-cygwin

$ ./gcc -v
Reading specs from ./../lib/gcc-lib/i686-pc-cygwin/3.1/specs
Configured with:
/cygdrive/d/data/gcc/gcc-3.1/configure --prefix=/usr/local/gcc-3.1
Thread model: single
gcc version 3.1

This is a Pentium 4 System with Microsoft Windows 2000 5.00.2195 Service
Pack 2.
$ uname -a
CYGWIN_NT-5.0 WATERFALL 1.3.10(0.51/3/2) 2002-02-25 11:14 i686 unknown

JEff Russell