gitignore updates

Ignore various build artifacts.

Change-Id: I8b0447bf66844c6cfd40b57da4564324dbd0322b
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/libmapper/.gitignore b/libmapper/.gitignore
index 216823b..23fb045 100644
--- a/libmapper/.gitignore
+++ b/libmapper/.gitignore
@@ -1,3 +1,4 @@
 *.so
 *.so.*
 *.o
+/.dirstamp