Added .gitignore file.

BUG=None
TEST=git ls-files -i --exclude-standard

Change-Id: Ic64b5cec6cb35aa8893db0aeb8e7c73bef93bcfc

.gitignore

@@ -0,0 +1,13 @@
+#
+# NOTE! Please use 'git ls-files -i --exclude-standard'
+# command after changing this file, to see if there are
+# any tracked files which get ignored after the change.
+#
+
+# Standard ignores
+*.o
+*~
+
+# Executables
+bsdiff
+bspatch