Add --debug=parse for option parsing debug

Adds log.h and debug.h to split the logging and debug bits out of
fio, so that the parser can use them.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/README b/README
index cf48c01..ef614a2 100644
--- a/README
+++ b/README
@@ -100,6 +100,7 @@
 	verify		Dump info related to IO verification
 	all		Enable all debug options
 	random		Dump info related to random offset generation
+	parse		Dump info related to option matching and parsing
 	? or help	Show available debug options.
 
 You can specify as many as you want, eg --debug=file,mem will enable