more informative curl error messages closes #905

This gets a bit redundant with some errors though:
```
=-=-= Installing hweak.1.1 =-=-=
hweak.1.1  Downloading http://aspellfr.free.fr/hweak/hweak-1.2.tar.gz
[ERROR] curl: code 404 while downloading http://aspellfr.free.fr/hweak/hweak-1.2.tar.gz
[ERROR] http://aspellfr.free.fr/hweak/hweak-1.2.tar.gz is not available
[ERROR] The compilation of hweak.1.1 failed.
```