std: Flatten the num directory to reflect the module layout

This makes it dissimilar to how core is structured on disk, but
more predictable on its own.

src/libstd/lib.rs

@@ -423,8 +423,8 @@ pub use core_collections::vec;
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use rustc_unicode::char;
 
-#[path = "num/f32.rs"]   pub mod f32;
-#[path = "num/f64.rs"]   pub mod f64;
+pub mod f32;
+pub mod f64;
 
 #[macro_use]
 pub mod thread;

src/tools/tidy/src/pal.rs

@@ -65,8 +65,8 @@ const EXCEPTION_PATHS: &'static [&'static str] = &[
     // temporary exceptions
     "src/libstd/rtdeps.rs", // Until rustbuild replaces make
     "src/libstd/path.rs",
-    "src/libstd/num/f32.rs",
-    "src/libstd/num/f64.rs",
+    "src/libstd/f32.rs",
+    "src/libstd/f64.rs",
     "src/libstd/sys_common/mod.rs",
     "src/libstd/sys_common/net.rs",
     "src/libterm", // Not sure how to make this crate portable, but test needs it