add check-c make target

This makes it easier to run locitest.
diff --git a/Makefile b/Makefile
index ab834be..63d28eb 100644
--- a/Makefile
+++ b/Makefile
@@ -89,6 +89,11 @@
 	PYTHONPATH=${LOXI_OUTPUT_DIR}/pyloxi:. python py_gen/tests/of12.py
 	PYTHONPATH=${LOXI_OUTPUT_DIR}/pyloxi:. python py_gen/tests/of13.py
 
+check-c: c
+	gcc -o ${LOXI_OUTPUT_DIR}/locitest/locitest ${LOXI_OUTPUT_DIR}/locitest/src/*.c ${LOXI_OUTPUT_DIR}/loci/src/*.c \
+		-I ${LOXI_OUTPUT_DIR}/loci/inc -I ${LOXI_OUTPUT_DIR}/locitest/inc -I ${LOXI_OUTPUT_DIR}/loci/src
+	${LOXI_OUTPUT_DIR}/locitest/locitest
+
 pylint:
 	pylint -E ${LOXI_PY_FILES}