Fix prelude.inc handling in .cabal to make new-install work

Hopefully fixes both #162 and #200.

brittany.cabal

@@ -25,6 +25,7 @@ extra-doc-files: {
 }
 extra-source-files: {
   src-literatetests/*.blt
+  srcinc/prelude.inc
 }
 
 source-repository head {
@@ -42,9 +43,8 @@ library {
     Haskell2010
   hs-source-dirs:
     src
-  install-includes: {
+  include-dirs:
-    srcinc/prelude.inc
+    srcinc
-  }
   exposed-modules: {
     Language.Haskell.Brittany
     Language.Haskell.Brittany.Internal
@@ -130,8 +130,6 @@ library {
     MultiWayIf
     KindSignatures
   }
-  include-dirs:
-    srcinc
 }
 
 executable brittany
@@ -179,6 +177,7 @@ executable brittany
     , filepath >=1.4.1.0 && <1.5
     }
   hs-source-dirs:      src-brittany
+  include-dirs:        srcinc
   default-language:    Haskell2010
   default-extensions: {
     CPP
@@ -249,6 +248,7 @@ test-suite unittests
   other-modules:    TestUtils
                     AsymptoticPerfTests
   hs-source-dirs:   src-unittests
+  include-dirs:     srcinc
   default-extensions: {
     CPP
 
@@ -321,6 +321,7 @@ test-suite littests
   main-is:          Main.hs
   other-modules:
   hs-source-dirs:   src-literatetests
+  include-dirs:     srcinc
   default-extensions: {
     CPP
 
@@ -362,6 +363,7 @@ test-suite libinterfacetests
   main-is:          Main.hs
   other-modules:
   hs-source-dirs:   src-libinterfacetests
+  include-dirs:     srcinc
   default-extensions: {
     FlexibleContexts
     FlexibleInstances