Tracker: A few more style fixes to IconCache

* Hilight => Highlight
Tracker: A few more style fixes to Utilities

* icon_size size => icon_size which (I've settled on which)
* fOrigBitmap => fOriginalBitmap
* resizeMask/resizeFlags => resizingMode (header and cpp match)
* error => result
* explicit NULL checks for pointers
* multi-line conditional ifs get {}'s
* rename result to more descriptive name when not status_t