i18n support and pt_BR translation

We have added i18n support to Leksah using the hgettext package. As hgettext is not very well supported in Windows [1], we have specified in the cabal file that it can only be compiled with hgettext on Linux. Since this is a bit experimental, we have also chosen to use a flag "loc" to enable compilation with i18n support.

At the time, compilation with i18n support can only be done using SetupLocale.lhs, as "runhaskell SetupLocale.lhs configure -floc", and likewise "build" and "install". This is because hgettext requires some changes to the default Setup file, so that cabal installs the translation files. As I couldn't figure out a way to selectively compile the regular Setup or the changes made for hgettext, I decided to put it into a separate file altogether.

Furthermore, we have worked to translate most of it to pt_BR. Translation can be tracked at https://www.transifex.com/projects/p/leksah/ .

Leksah running in pt_BR can be seen here:
![LEKSAH - Screenshot - 03072013 - 12:37:35 AM](https://f.cloud.github.com/assets/711072/319907/0e96e282-98f6-11e2-8d81-188e98dc7326.png)

[1] http://www.haskell.org/haskellwiki/Internationalization_of_Haskell_programs#Using_GNU_gettext