gst-uninstalled: add video and base library paths from -bad

https://bugzilla.gnome.org/show_bug.cgi?id=732770
tests: fix locking in gstpoll unit test

The mutex needs to be locked when g_cond_wait*() is
called.
libs: gstcheck: init and clear global mutex and cond variables
libs: gstcheck: check that mutex is locked before g_cond_wait*() is called

Sanity check to catch problems in unit test.
fdsrc: fix error setting when uri is invalid

Elements should always set the GError