Travis: Test GHC 8.4.2

While I was in town, I also:

* Added a cabal.project file
* Updated .gitignore to include cabal new-build artifacts

.gitignore

-dist-install
 dist
+dist-*
+cabal-dev
+*.o
+*.hi
+*.chi
+*.chs.h
+*.dyn_o
+*.dyn_hi
+.hpc
+.hsenv
+.cabal-sandbox/
+cabal.sandbox.config
+*.prof
+*.aux
+*.hp
+*.eventlog
+.stack-work/
+cabal.project.local
+cabal.project.local~
+.HTF/
+.ghc.environment.*

.travis.yml

 # This Travis job script has been generated by a script via
 #
-#   runghc make_travis_yml_2.hs 'hsc2hs.cabal'
+#   runghc make_travis_yml_2.hs '-o' '.travis.yml' 'cabal.project'
 #
 # For more information, see https://github.com/hvr/multi-ghc-travis
 #
@@ -54,12 +54,15 @@ matrix:
     - compiler: "ghc-8.2.2"
     # env: TEST=--disable-tests BENCH=--disable-benchmarks
       addons: {apt: {packages: [ghc-ppa-tools,cabal-install-head,ghc-8.2.2], sources: [hvr-ghc]}}
-    - compiler: "ghc-8.4.1"
+    - compiler: "ghc-8.4.2"
+    # env: TEST=--disable-tests BENCH=--disable-benchmarks
+      addons: {apt: {packages: [ghc-ppa-tools,cabal-install-head,ghc-8.4.2], sources: [hvr-ghc]}}
+    - compiler: "ghc-head"
       env: GHCHEAD=true
-      addons: {apt: {packages: [ghc-ppa-tools,cabal-install-head,ghc-8.4.1], sources: [hvr-ghc]}}
+      addons: {apt: {packages: [ghc-ppa-tools,cabal-install-head,ghc-head], sources: [hvr-ghc]}}
 
   allow_failures:
-    - compiler: "ghc-8.4.1"
+    - compiler: "ghc-head"
 
 before_install:
   - HC=${CC}
@@ -132,5 +135,5 @@ script:
   # cabal check
   - (cd hsc2hs-* && cabal check)
 
-# REGENDATA ["hsc2hs.cabal"]
+# REGENDATA ["-o",".travis.yml","cabal.project"]
 # EOF

cabal.project

+packages: .

hsc2hs.cabal

@@ -23,7 +23,7 @@ Category: Development
 Data-Files: template-hsc.h
 build-type: Simple
 cabal-version: >=1.10
-tested-with: GHC==8.2.1, GHC==8.0.2, GHC==7.10.3, GHC==7.8.4, GHC==7.6.3, GHC==7.4.2, GHC==7.2.2, GHC==7.0.4
+tested-with: GHC==8.4.2, GHC==8.2.2, GHC==8.0.2, GHC==7.10.3, GHC==7.8.4, GHC==7.6.3, GHC==7.4.2, GHC==7.2.2, GHC==7.0.4
 
 extra-source-files:
   changelog.md