Move out gbproxy to its own subdir

Change-Id: I2cc98d3a276d953609bbbbaa9782a0112687791e
diff --git a/src/Makefile.am b/src/Makefile.am
index d2dcb9f..024938d 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -1,3 +1,4 @@
 SUBDIRS = \
 	gprs \
+	gbproxy \
 	$(NULL)