Remove reexports from ghc-boot, help bootstrap with GHC 8.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

compiler/ghc.cabal.in

@@ -58,6 +58,7 @@ Library
                    hpc        == 0.6.*,
                    transformers == 0.5.*,
                    ghc-boot   == @ProjectVersionMunged@,
+                   ghc-boot-th == @ProjectVersionMunged@,
                    hoopl      >= 3.10.2 && < 3.11
 
     if os(windows)

libraries/ghc-boot/ghc-boot.cabal.in

@@ -40,10 +40,6 @@ Library
             GHC.PackageDb
             GHC.Serialized
 
-    reexported-modules:
-            GHC.LanguageExtensions.Type,
-            GHC.Lexeme
-
     build-depends: base       >= 4.7 && < 4.10,
                    binary     == 0.8.*,
                    bytestring == 0.10.*,