Support more sphinx-build versions in configure script
Support more sphinx-build versions in configure script

`sphinx-build` on CentOS
(`python-sphinx10-doc-1.0.8-1.el6.centos.noarch`) responds with this on
`stderr`:
```
$ sphinx-1.0-build --version
Sphinx v1.0.8
Usage: /usr/bin/sphinx-1.0-build [options] sourcedir outdir
[filenames...]
Options: -b <builder> -- builder to use; default is html
         -a        -- write all files; default is to only write new and
changed files
...
Modi:
* without -a and without filenames, write new and changed files.
* with -a, write all files.
* with filenames, write these.
```

This should make it work for the old and the new format.

Test Plan:
```
$ echo "Sphinx (sphinx-build) 1.0.1" | sed 's/Sphinx\(
(sphinx-build)\)\? v\?\([0-9]\.[0-9]\.[0-9]\)/\2/'
1.0.1
$ echo "Sphinx v1.0.1" | sed 's/Sphinx\( (sphinx-build)\)\?
v\?\([0-9]\.[0-9]\.[0-9]\)/\2/'
1.0.1
```

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: thomie, erikd

Differential Revision: https://phabricator.haskell.org/D1361

ezyang/ghc,ezyang/ghc,GaloisInc/halvm-ghc,elieux/ghc,AlexanderPankiv/ghc,oldmanmike/ghc,elieux/ghc,tjakway/ghcjvm,olsner/ghc,tjakway/ghcjvm,olsner/ghc,AlexanderPankiv/ghc,gridaphobe/ghc,mettekou/ghc,oldmanmike/ghc,da-x/ghc,siddhanathan/ghc,da-x/ghc,elieux/ghc,ezyang/ghc,gridaphobe/ghc,snoyberg/ghc,da-x/ghc,mettekou/ghc,da-x/ghc,mcschroeder/ghc,elieux/ghc,sgillespie/ghc,nushio3/ghc,snoyberg/ghc,mcschroeder/ghc,vikraman/ghc,siddhanathan/ghc,GaloisInc/halvm-ghc,sgillespie/ghc,vTurbine/ghc,ezyang/ghc,da-x/ghc,olsner/ghc,snoyberg/ghc,tjakway/ghcjvm,mcschroeder/ghc,ezyang/ghc,siddhanathan/ghc,AlexanderPankiv/ghc,oldmanmike/ghc,tjakway/ghcjvm,nushio3/ghc,sdiehl/ghc,shlevy/ghc,ezyang/ghc,da-x/ghc,gridaphobe/ghc,tjakway/ghcjvm,shlevy/ghc,gridaphobe/ghc,shlevy/ghc,siddhanathan/ghc,mettekou/ghc,vikraman/ghc,sdiehl/ghc,oldmanmike/ghc,mettekou/ghc,shlevy/ghc,mcschroeder/ghc,AlexanderPankiv/ghc,sdiehl/ghc,vikraman/ghc,AlexanderPankiv/ghc,vikraman/ghc,olsner/ghc,shlevy/ghc,AlexanderPankiv/ghc,vikraman/ghc,GaloisInc/halvm-ghc,oldmanmike/ghc,GaloisInc/halvm-ghc,mcschroeder/ghc,vikraman/ghc,sgillespie/ghc,nushio3/ghc,AlexanderPankiv/ghc,elieux/ghc,vTurbine/ghc,nushio3/ghc,siddhanathan/ghc,vTurbine/ghc,oldmanmike/ghc,snoyberg/ghc,vTurbine/ghc,snoyberg/ghc,GaloisInc/halvm-ghc,snoyberg/ghc,nushio3/ghc,mcschroeder/ghc,elieux/ghc,vTurbine/ghc,GaloisInc/halvm-ghc,sdiehl/ghc,mcschroeder/ghc,mettekou/ghc,snoyberg/ghc,vTurbine/ghc,tjakway/ghcjvm,siddhanathan/ghc,gridaphobe/ghc,sdiehl/ghc,vikraman/ghc,tjakway/ghcjvm,GaloisInc/halvm-ghc,olsner/ghc,mettekou/ghc,shlevy/ghc,sdiehl/ghc,sgillespie/ghc,shlevy/ghc,nushio3/ghc,elieux/ghc,sgillespie/ghc,sgillespie/ghc,vTurbine/ghc,gridaphobe/ghc,da-x/ghc,sgillespie/ghc,gridaphobe/ghc,sdiehl/ghc,oldmanmike/ghc,nushio3/ghc,mettekou/ghc,siddhanathan/ghc,ezyang/ghc,olsner/ghc,olsner/ghc