Implement optional module loading

The syntax is:

using? cli

Now each module use results in two bool variables: <module>.loaded and
<module>.configured.

Also implement variable visibility (the above two variables are limited
to project).

1 files changed, 4 insertions, 2 deletions

diff --git a/build/config/module b/build/config/module
index 58d9814..530fa7b 100644
--- a/build/config/module
+++ b/build/config/module
@@ -6,15 +6,17 @@
 #define BUILD_CONFIG_MODULE
 
 #include <build/types>
+#include <build/utility>
+
 #include <build/module>
 
 namespace build
 {
   namespace config
   {
-    extern "C" void
+    extern "C" bool
     config_init (
-      scope&, scope&, const location&, std::unique_ptr<module>&, bool);
+    scope&, scope&, const location&, unique_ptr<module>&, bool, bool);
   }
 }