fix: undefined symbol: g_type_name

Always override gtk-dialogs-use-header property value to FALSE

Setting it to TRUE will break save dialog.
Fix for #13.

Fix for black borders around some application windows

Hiding GtkHeaderBar when custom title wasn't set

This commit should fix #8 while not breaking other things

Removed questionable code to hide GtkHeaderBar (fix for #5)

hide only GtkHeaderBar widget (fix for #4)

reintroduce deprecated macros G_TYPE_INSTANCE_GET_PRIVATE

Merge pull request #1 from toluschr/master

Fixed: Title being present twice

Add TODO list

Fix compiler flags handling

Filter out -fPIE for libraries, make sure we always add include paths to
CFLAGS (use overrides), and append -fPIC only for libraries.