Preparation patch for KMSG.

Preparation patch for KMSG.

This is the first of a series of patches which implement KMSG, which is
a replacement for old android log devices, serving as a fast dlog backend.

The patches are not applied onto the original printk file, but to a copy.
This is to keep the codebase maintainable. Any future backports will be
able to merge conflictlessly and preprocessor macroes are prevented from
excessive piling in the original file.

This patch adds a MULTIPLE_KMSG config flag and creates the copy of the
printk file which will serve as the target of subsequent KMSG patches.

Change-Id: Idead56234820ff9d024da88310dc2e505cf051d0
Signed-off-by: Michal Bloch <m.bloch@samsung.com>