[ issue 1156 ] Removed Agda.Utils.Monad.bracket

The function generates a warning with mtl 2.2.1.
[ issue 1156 ] Cosmetic changes
Merge branch 'maint-2.4.2'
[ issue 1156 ] Fixed

I centralised all the stuff related to Control.Monad.Except from
the mtl package in the module Agda.Utils.Except.
Merge branch 'maint-2.4.2'
[ issue 1156 ] Support for previous versions of mtl and transformers
Merge branch 'maint-2.4.2'
[ issue 1156 ] Minor changes
Merge branch 'maint-2.4.2'
[ fix-agda-whitespace ] Support for text 1.2.*
Merge branch 'maint-2.4.2'
[ issue 1156 ] Replaced data constructor by function

We defined the `mkExceptT` function to be used instead of the data
constructor `ExceptT`/`ErrorT`.
Merge branch 'maint-2.4.2'
[ Cabal ] Sorted dependencies
[ issue 1279 ] haskell-src-exts 1.16.0 removed UnGuardedAlt

See https://github.com/haskell-suite/haskell-src-exts/commit/031c88c77f0a98e80cc4925f6fae43cb6b2d3485
[ issue 1279 ] haskell-src-exts 1.16.0 removed UnBangedTy

See https://github.com/haskell-suite/haskell-src-exts/commit/1a99f0e8c8e9513ac2d07c9eae2ffd6122513fe9
[ issue 1279 ] Added type signatures
[ issue 1279 ] haskell-src-exts 1.16.0 added support for safe imports

See https://github.com/haskell-suite/haskell-src-exts/commit/7d789cc11fca73304699a3404bf72eb56014ba8b
[ issue 1279 ] Added type signatures
[ issue 1279 ] Fixed typo