docs: clarify supported GHC versions

MANUAL.md

@@ -33,14 +33,14 @@ hledger works on linux, mac and windows. You can fund ready-to-run
 binaries of the latest release - see the [download page](DOWNLOAD.html).
 
 Otherwise, build the latest release from Hackage using cabal-install.
-Ensure you have [GHC](http://hackage.haskell.org/ghc/) (7.0 or greater) or
-the [Haskell Platform](http://hackage.haskell.org/platform/) installed,
-then:
+Ensure you have [GHC](http://hackage.haskell.org/ghc/) (6.12.3 or greater;
+7.0 or greater for hledger-web) or the
+[Haskell Platform](http://hackage.haskell.org/platform/) installed, then:
 
     $ cabal update
     $ cabal install hledger
 
-To also install the web interface (which can be a bit harder) do:
+To also install the web interface, do:
 
     $ cabal install hledger-web
 
@@ -1259,8 +1259,9 @@ or get help.
   If not, `cabal update` and try again.
 
 - **Do you have a new enough version of GHC ?**  
-  Run `ghc --version`. hledger requires at least GHC 6.12.3 - or possibly
-  7.0 - and on [some platforms](#5551), 7.2.1.
+  Run `ghc --version`. hledger requires GHC 6.12.3 or greater
+  (on [some platforms](#5551), 7.2.1 can be helpful) and hledger-web
+  requires 7.0 or greater.
 
 - **Do you have a new enough version of cabal ?**  
   Avoid ancient versions.  `cabal --version` should report at least

hledger-lib/hledger-lib.cabal

@@ -17,7 +17,7 @@ maintainer:     Simon Michael <simon@joyful.com>
 homepage:       http://hledger.org
 bug-reports:    http://code.google.com/p/hledger/issues
 stability:      beta
-tested-with:    GHC==7.0, GHC==7.2
+tested-with:    GHC==6.12.3, GHC==7.0.4, GHC==7.2.2, GHC==7.4.1
 cabal-version:  >= 1.6
 build-type:     Simple
 -- data-dir:       data

hledger-web/hledger-web.cabal

@@ -17,7 +17,7 @@ maintainer:     Simon Michael <simon@joyful.com>
 homepage:       http://hledger.org
 bug-reports:    http://code.google.com/p/hledger/issues
 stability:      beta
-tested-with:    GHC==7.0, GHC==7.2
+tested-with:    GHC==7.0, GHC==7.2, GHC==7.4.1
 cabal-version:  >= 1.6
 build-type:     Simple
 extra-tmp-files:

hledger/hledger.cabal

@@ -17,7 +17,7 @@ maintainer:     Simon Michael <simon@joyful.com>
 homepage:       http://hledger.org
 bug-reports:    http://code.google.com/p/hledger/issues
 stability:      beta
-tested-with:    GHC==7.0, GHC==7.2
+tested-with:    GHC==6.12.3, GHC==7.0.4, GHC==7.2.2, GHC==7.4.1
 cabal-version:  >= 1.8
 build-type:     Simple
 -- data-dir:       data