Implement common logging function

When used as a library, it's desirable to be able to suppress logging,
or pipe logging through a different path.  This commit changes behavior
such that logging is disabled by default, and introduces 2 new methods,
cper_set_log_stdio and cper_set_log_custom.

These allow library integrators to specify their logging mode.  In
practice, this also allows fuzzing to run faster by not printing errors
to the log.

Change-Id: I941476627bc9b8261ba5f6c0b2b2338fdf931dd2
Signed-off-by: Ed Tanous <etanous@nvidia.com>
diff --git a/generator/cper-generate.c b/generator/cper-generate.c
index 8675a78..b1b105b 100644
--- a/generator/cper-generate.c
+++ b/generator/cper-generate.c
@@ -7,6 +7,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <libcper/log.h>
 #include <libcper/Cper.h>
 #include <libcper/generator/gen-utils.h>
 #include <libcper/generator/sections/gen-section.h>