libgui/SF: Fix some code warnings

A couple of fixes to satisfy the Eclipse static code analysis tool.
- Initialize all members in constructors
- Remove unused forward declarations
- Add parentheses when combining logical and bitwise operators
- Fix a case statement with no break (it was intentional)

Change-Id: Icecb8cc98c6f58b97ab33fffb621f0edc33a7d3c