Add libnpcommon.a file to .gitignore

.gitignore

@@ -191,6 +191,7 @@ NP-VERSION-FILE
 /plugins/.libs
 /plugins/Makefile
 /plugins/Makefile.in
+/plugins/libnpcommon.a
 /plugins/negate
 /plugins/stamp-h*
 /plugins/urlize