Extra slashes in ~grep/po/Makefile

[Steve Kenton]

grep-2.5.4-20080209b

There are several places in the Makefile for the po directory that use 
the following construct.
It only occurs in the po directory, not any other directory under grep 
source tree. And, is
seems to be a fairly old bug which has occurred in previous versions of 
grep, not just current.

$(var1)/$(var2) when $var2 is already an absolute path with a leading slash.

After evaluation this results in a path with double slashes, which is 
normally harmless,
but on Cygwin this is interpreted as an attempt to use a network path 
and error out.

For example, configuring grep with --prefix=/snap/build results in the 
following error for make install

mkdir -p -- //snap/build/local/share
mkdir: cannot create directory `//snap': No such host or network path

I tried to work out a patch but quickly lost my way in the substitution 
involved in configure and Makefile.in
Hopefully someone which a clearer understanding can nip this one at it's 
source

FYI - Steve Kenton