Fix configure failing because of missing m4 directory.
Fix configure failing because of missing m4 directory.

This was broken by the conversion to git, since it cannot store empty
directories.

prajnashi/gst-openmax,mrchapp/gst-openmax,mrchapp/gst-openmax,mrchapp/gst-openmax,felipec/gst-openmax,mrchapp/gst-openmax-devel,PPCDroid/external-gst-openmax,mrchapp/gst-openmax-devel,PPCDroid/external-gst-openmax,freedesktop-unofficial-mirror/gstreamer__attic__gst-openmax,felipec/gst-openmax,matsu/gst-openmax,matsu/gst-openmax,prajnashi/gst-openmax,freedesktop-unofficial-mirror/gstreamer__attic__gst-openmax,mrchapp/gst-openmax-devel