Simplify / clean up some menu code
Add strfree to reduce explicit use of strunzone/string_null
menu: #undef IMPLEMENTATION
Header police
Fix an error caused by the selection of the first cvar before the cvarlist is loaded; also fix another small issue when restarting the menu caused by nItems getting initialized to 42 in the listBox class (WTF!)
Avoid loading lists of demos, screenshots and music tracks when the menu starts, they are loaded when they get displayed anyway
#includes: cleanup menu
Require semicolon or definition following `METHOD`
Special handling of the scrolling with mouse wheel isn't needed anymore in the screenshotlist
Small cleanup
Merge remote-tracking branch 'origin/master' into terencehill/listbox_item_highlight
#include base classes
Sort menu classes
Listbox / Picker: Implement item fading in a different way so that it gets influenced by menu_slowmo
Merge CLASS and EXTENDS, #define NEW(cname) (spawn##cname())
Add skin attributes for listbox focused items and allow customization of the fade effect
Listbox: highlight item under the cursor
Unify boolean constants TRUE -> true FALSE -> false
Replace `vector_[xyz]` with `vector.[xyz]` where possible
Rename menu files to be consistent *.h -> *.qh *.c -> *.qc