Add a default `.ghci' file

This options file for ghci preseeds the correct include paths, so that
interactive sessions don't need to always pass these args.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>

.ghci

+:set -ihtools -ihtest

Makefile.am

@@ -759,7 +759,8 @@ EXTRA_DIST = \
 	$(HS_PROG_SRCS) \
 	htools/lint-hints.hs \
 	htest/cli-tests-defs.sh \
-	htest/offline-test.sh
+	htest/offline-test.sh \
+	.ghci
 
 man_MANS = \
 	man/ganeti-cleaner.8 \