Fix uncontroversial cabal check warnings

We will have to make reflex-platform contain optimized package sets
before we get rid of `-O2`.

reflex.cabal

@@ -9,7 +9,7 @@ Maintainer: [email protected]
 Stability: Experimental
 Category: FRP
 Build-type: Simple
-Cabal-version: >=1.22
+Cabal-version: 1.22
 homepage: https://reflex-frp.org
 bug-reports: https://github.com/reflex-frp/reflex/issues
 extra-source-files:
@@ -47,6 +47,7 @@ flag split-these
   default:     True
 
 library
+  default-language: Haskell2010
   hs-source-dirs: src
   build-depends:
     MemoTrie == 0.6.*,
@@ -170,6 +171,7 @@ library
     build-depends: ghcjs-base
 
 test-suite semantics
+  default-language: Haskell2010
   type: exitcode-stdio-1.0
   main-is: semantics.hs
   hs-source-dirs: test
@@ -195,6 +197,7 @@ test-suite semantics
     Reflex.TestPlan
 
 test-suite CrossImpl
+  default-language: Haskell2010
   type: exitcode-stdio-1.0
   main-is: Reflex/Test/CrossImpl.hs
   hs-source-dirs: test
@@ -216,6 +219,7 @@ test-suite CrossImpl
     Reflex.Plan.Pure
 
 test-suite hlint
+  default-language: Haskell2010
   type: exitcode-stdio-1.0
   main-is: hlint.hs
   hs-source-dirs: test
@@ -228,6 +232,7 @@ test-suite hlint
     buildable: False
 
 test-suite EventWriterT
+  default-language: Haskell2010
   type: exitcode-stdio-1.0
   main-is: EventWriterT.hs
   hs-source-dirs: test
@@ -255,6 +260,7 @@ test-suite EventWriterT
 
 
 test-suite RequesterT
+  default-language: Haskell2010
   type: exitcode-stdio-1.0
   main-is: RequesterT.hs
   hs-source-dirs: test
@@ -279,6 +285,7 @@ test-suite RequesterT
     Test.Run
 
 test-suite QueryT
+  default-language: Haskell2010
   type: exitcode-stdio-1.0
   main-is: QueryT.hs
   hs-source-dirs: test
@@ -306,6 +313,7 @@ test-suite QueryT
     Reflex.Plan.Pure
 
 test-suite GC-Semantics
+  default-language: Haskell2010
   type: exitcode-stdio-1.0
   main-is: GC.hs
   hs-source-dirs: test
@@ -331,6 +339,7 @@ test-suite GC-Semantics
     Test.Run
 
 test-suite rootCleanup
+  default-language: Haskell2010
   type: exitcode-stdio-1.0
   main-is: rootCleanup.hs
   hs-source-dirs: test
@@ -348,6 +357,7 @@ test-suite rootCleanup
     Test.Run
 
 benchmark spider-bench
+  default-language: Haskell2010
   type: exitcode-stdio-1.0
   hs-source-dirs: bench test
   main-is: Main.hs
@@ -372,6 +382,7 @@ benchmark spider-bench
     Reflex.Bench.Focused
 
 benchmark saulzar-bench
+  default-language: Haskell2010
   type: exitcode-stdio-1.0
   hs-source-dirs: bench test
   c-sources: bench-cbits/checkCapability.c