Make AM_CFLAGS matter in src/ again
Make AM_CFLAGS matter in src/ again

Setting libmcd_convenience_la_CFLAGS to any value, ever, disables use
of AM_CFLAGS for those source files. INCLUDES is what we want here.

freedesktop-unofficial-mirror/telepathy__telepathy-mission-control,freedesktop-unofficial-mirror/telepathy__telepathy-mission-control,freedesktop-unofficial-mirror/telepathy__telepathy-mission-control,freedesktop-unofficial-mirror/telepathy__telepathy-mission-control