mel: remove *_MIRROR from SRC_URI vardeps

Changing one of the _MIRROR variables (e.g. APACHE_MIRROR) only changes where
we're downloading something from, not what we're downloading. We don't want to
force a refetch/rebuild when the mirror variables change, so exclude it from
the SRC_URI vardeps.

Signed-off-by: Christopher Larson <kergoth@gmail.com>
systemtap: drop seemingly unnecessary -lpthread

Signed-off-by: Christopher Larson <kergoth@gmail.com>
core-tools-profile: drop lttng 0.x support bits

We no longer support any machines that require this.

Signed-off-by: Christopher Larson <kergoth@gmail.com>
subversion: drop APACHE_MIRROR override

This overridden value is already in MIRRORS.

Signed-off-by: Christopher Larson <kergoth@gmail.com>
libsdl: drop gl bits via DISTRO_FEATURES

Also obey mel override, drop unnecessary PR.

Signed-off-by: Christopher Larson <kergoth@gmail.com>
meta-mel: obey mel override everywhere

Signed-off-by: Christopher Larson <kergoth@gmail.com>