[config] GTK backend is long gone
[config] Nothing uses those colors anymore
Import UTF8-CPP 2.3.4

http://sourceforge.net/projects/utfcpp/files/utf8cpp_2x/Release%202.3.4/utf8_v2_3_4.zip

Part of #12.
Use UTF8-CPP instead of GLib for charset conversion

Part of #12.
Drop GLib dependency from the core library

Fixes #12.
Unnecessary if's