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>
diff --git a/phosphor-logging.pc.in b/phosphor-logging.pc.in
index 228246a..6ab5119 100644
--- a/phosphor-logging.pc.in
+++ b/phosphor-logging.pc.in
@@ -9,5 +9,5 @@
 Version: @VERSION@
 Requires: @AX_PACKAGE_REQUIRES@
 Requires.private: @AX_PACKAGE_REQUIRES_PRIVATE@
-Libs:
+Libs: -L@libdir@ -lphosphor_logging
 Cflags: -I@includedir@