Create libphosphor-logging library

The commit function would be too big to hold on the
header file. Move it to a library and update the
phosphos-logging.pc file for users to link against it.
Add dependency to libsdbusplus as the commit interface
would make use of the transaction id support.

Change-Id: I237b15e35a633f1da9bf3401b5bf754154f132db
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
4 files changed