Move `/includes` to `/rts/include`, sort per package betterwip/organize-headers

In order to make the packages in this repo "reinstallable", we need to
associate source code with a specific packages. Having a top level
`/includes` dir that mixes concerns (which packages' includes?) gets in
the way of this.

To start, I have moved everything to `rts/`, which is mostly correct.
There are a few things however that really don't belong in the rts (like
the generated constants haskell type, `CodeGen.Platform.h`). Those
needed to be manually adjusted.

Things of note:

 - No symlinking for sake of windows, so we hard-link at configure time.

 - `CodeGen.Platform.h` no longer as `.hs` extension (in addition to
   being moved to `compiler/`) so as not to confuse anyone, since it is
   next to Haskell files.

 - Blanket `-Iincludes` is gone in both build systems, include paths now
   more strictly respect per-package dependencies.

 - `deriveConstants` has been taught to not require a `--target-os` flag
   when generating the platform-agnostic Haskell type. Make takes
   advantage of this, but Hadrian has yet to.

1 files changed, 1 insertions, 1 deletions

diff --git a/compiler/GHC/Platform/SPARC.hs b/compiler/GHC/Platform/SPARC.hs
index b1dad08837..d0ab5fe41a 100644
--- a/compiler/GHC/Platform/SPARC.hs
+++ b/compiler/GHC/Platform/SPARC.hs
@@ -6,5 +6,5 @@ import GHC.Prelude
 
 #define MACHREGS_NO_REGS 0
 #define MACHREGS_sparc 1
-#include "../../../includes/CodeGen.Platform.hs"
+#include "CodeGen.Platform.h"