lowmemorykiller: make default lowmemorykiller debug message useful

lowmemorykiller debug messages are inscrutable and mostly useful
for debugging the lowmemorykiller, not explaining why a process
was killed.  Make the messages more useful by prefixing them
with "lowmemorykiller: " and explaining in more readable terms
what was killed, who it was killed for, and why it was killed.

The messages now look like:
[   76.997631] lowmemorykiller: Killing 'droid.gallery3d' (2172), adj 1000,
[   76.997635]    to free 27436kB on behalf of 'kswapd0' (29) because
[   76.997638]    cache 122624kB is below limit 122880kB for oom_score_adj 1000
[   76.997641]    Free memory is -53356kB above reserved

A negative number for free memory above reserved means some of the
reserved memory has been used and is being regenerated by kswapd,
which is likely what called the shrinkers.

Bug: 17871993
Change-Id: I1fe983381e73e124b90aa5d91cb66e55eaca390f
Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: Naveen Ramaraj <nramaraj@codeaurora.org>
lowmemorykiller: enhance debug information

Add extra debug information to make it easier to both determine
why the lowmemorykiller killed a process and to help find the source
of memory leaks.

Also increase the debug level for "select" statements to help prevent
flooding the log.

Bug: 17871993
Change-Id: I3b6876c5ecdf192ecc271aed3f37579f66d47a08
Signed-off-by: Liam Mark <lmark@codeaurora.org>
Signed-off-by: Naveen Ramaraj <nramaraj@codeaurora.org>
Signed-off-by: Iliyan Malchev <malchev@google.com>

Conflicts:
	drivers/staging/android/lowmemorykiller.c
kgsl: do not vmap/memset to zero-out pages

b/18402205 External reports: Video playback failing on Flo after upgrade to
	   Lollipop

Change-Id: I358328ba2bd543d77e4218f32b0695c2f6f6e6c9
Signed-off-by: Iliyan Malchev <malchev@google.com>