i18n

- Added en-US.h, which will be a header file full of string defines.
- Added logic to i18n.h to include en-US.h based on cmake command
  line argument (cmake ... -DPACKAGE_LANGUAGE=1).
- Added one sample string.

cmake.h.in

@@ -9,6 +9,15 @@
 #define PACKAGE_VERSION   "${PACKAGE_VERSION}"
 #define PACKAGE_STRING    "${PACKAGE_STRING}"
 
+/* Localization */
+#define PACKAGE_LANGUAGE  1
+#define LANGUAGE_EN_US 1
+
+/*
+Override PACKAGE_LANGUAGE, then
+#define LANGUAGE_XX_YY 2
+*/
+
 /* git information */
 #cmakedefine HAVE_COMMIT