[Agda] Agda and GHC 7.8

[Jan Stolarek]

> Which is the output of
>
> $ ./configure
>
> ?

Sorry for being too brief earlier. Running `make` seems to succeed, as it ends with suggestion to 
run `./configure`. Running `./configure` produces this:

```
checking for gcc... gcc
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables...
checking whether we are cross compiling... no
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ISO C89... none needed
checking for ghc... ghc
checking for ghc version... 7.8.3
checking for alex... alex
checking for alex version... 3.1.3
checking for happy... happy
checking for happy version... 1.19.4
checking for cpphs... cpphs
checking for cpphs version... 1.18.5
checking for haddock... haddock
checking for haddock version... 2.14.3
checking for latex... latex
checking for pdflatex... pdflatex
checking for a BSD-compatible install... /usr/bin/install -c
checking for wget... wget
checking for false... false
checking for find... find
checking for diff... diff
checking for darcs... no
checking for mkdir... mkdir
checking for runhaskell... runhaskell
configure: creating ./config.status
config.status: creating mk/config.mk
```

Then running `cabal install` produces the error I posted earlier. 

> One problem you might run into is the Cabal 1.16.* incompatibility
> with GHC 7.8.
```
$ cabal --version
cabal-install version 1.20.0.3
using version 1.20.0.2 of the Cabal library
```

These are the latest stable versions, installed yesterday.

> Unfortunately the Agda/Cabal/GHC ecosystem is complex enough for there
> to be failure points that aren't Agda bugs. 
True. But that argument could be used to refute any report that "X package does not compile". So 
while it's possible that Agda only exposes some underlying problem in GHC or Cabal (or my 
system), I am only experiencing this problem with Agda, which makes me think that Agda is the 
culprit.

Janek