Generated makefile's clean targets Windows binaries

[grepwood]

make clean does:

Making clean in plugins
test -z "" || rm -f
test -z "" || rm -f
rm -rf .libs _libs
test -z "" || rm -f
rm -f _.o
rm -f *.lo
Making clean in src
rm -f acmtool
rm -rf .libs _libs
test -z "libacm.la" || rm -f libacm.la
rm -f "./so_locations"
rm -f *.o
rm -f *.lo
Making clean in .
rm -rf .libs libs
rm -f in_libacm.dll acmtool.exe core core.
rm -f *.lo