Otherwise, each source file that includes the header will create a
new definition, which are usually merged together by the linker.
Multiple definitions of an object is not allowed in ISO C.
The use of the application instance handle global variable was
inconsistent throughout the windows frontend.
By rationalising the passing of these handles it showed that some of
the toolbar and throbber parent handles were also setup wrong giving
odd offset behaviour.
All these issues have been addressed and the throbber is now in the
correct position.
