use gnu indent to enforce coding style and adapt source

- indent options are listed in ./.indent.pro
 - use test case to run indent

tests/indent.sh

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+ret=0
+for f in ../**/*.c ../**/*.h; do
+	case $f in
+		../**/CMakeFiles/**/*)
+			;;
+		*)
+			INDENT_PROFILE=../.indent.pro indent -st $f | diff -u $f -
+			ret=$((ret+$?))
+			;;
+	esac
+done
+
+exit $ret