build: Detect The platform at conifgure time
build: Detect The platform at conifgure time

This patch adds $platform variable to the configure script and
OS_WINDOWS AM variable which can be used with Makefile.am files

freedesktop-unofficial-mirror/telepathy__telepathy-salut,freedesktop-unofficial-mirror/telepathy__telepathy-salut,freedesktop-unofficial-mirror/telepathy__telepathy-salut,freedesktop-unofficial-mirror/telepathy__telepathy-salut