Modernize loops (WOCommon, 05a1822)

Remove deprecated WO_ENUMERATE/foreach macros and modernize all loops to use the new Objective-C 2.0 fast enumeration construct. The WO_REVERSE_ENUMERATE and WO_KEY_ENUMERATE macros are retained because they have no equivalent language-level constructs.

Signed-off-by: Greg Hurrell <greg@hurrell.net>