CONFIGURE: add "--enable-minimal-flags"

This will turn off automagic adding of flags that might be unwanted
such as "-g" or "-pipe".
MAKE: backwards compat for old libtool
Implemented clear functionality for DCC download manager. Created clear button in DCC downloaded manager interface.
Updater: fix download links
Fixed coding style and clearified some comments, following arnavion suggestions
Permit dot-less domain names

Fixes #523
Python: Add support for attributes in hooks
Merge pull request #680 from staticshock/dotless-domains

Permit dot-less domain names
Python: Use keywords for attributes in emit_print()
Merge xchat r1525

Fixes possible crash
Merge pull request #689 from hexchat/python-attributes

Python: Add support for attributes in hooks
Python: return hooks with PyLong_FromVoidPtr

Fixes #685
Removed restriction that disabled the clear button if at least one transfer item was selected in dcc download manager.
Move optimization settings from all subsequent projects to hexchat.props
Upd: Properly handle http errors

Also some cleanup of some old code and comments
Merge pull request #679 from hasufell/libtool

MAKE: backwards compat for old libtool
Use system's libsexy by default

It will still fallback to static
Python: Fix callbacks for the "special" print hooks
Fix some warnings
Tweak cli output and fix related warnings