Adjusting the module layout to match the C library includes better.

This makes it so that if you needed to include stdio.h in C now
you would:

   use pact::stdio::*;

src/c/mod.rs

@@ -3,18 +3,10 @@
 //! this library is as up-to-date as it can be.
 
 
-mod errno;
-mod math;
-mod stddef;
-mod stdlib;
-mod string;
-mod time;
-
-
-
-pub use self::errno::*;
-pub use self::math::*;
-pub use self::stddef::*;
-pub use self::stdlib::*;
-pub use self::string::*;
-pub use self::time::*;
+pub mod errno;
+pub mod math;
+pub mod stddef;
+pub mod stdlib;
+pub mod stdio;
+pub mod string;
+pub mod time;