Rewrite the c module loader, adding a search path (fixes #1050)

Note: also removes the restriction that only fused games can load libraries from
their save folders.

--HG--
branch : minor

src/modules/filesystem/Filesystem.h

@@ -261,6 +261,7 @@ public:
 	// Require path accessors
 	// Not const because it's R/W
 	virtual std::vector<std::string> &getRequirePath() = 0;
+	virtual std::vector<std::string> &getCRequirePath() = 0;
 
 	/**
 	 * Allows a full (OS-dependent) path to be used with Filesystem::mount.