It's now crossplatform wrapper for std::system opening of a file/path/url.
It returns an int just like std::system, 0 means it worked.
It's static so you don't need to gViewerWindow->getWindow() anymore,
honestly it should've been static in the first place.
Clean up other code to use this function because duplicate code sucks.
# Conflicts:
# indra/llwindow/llwindowmacosx.h
# indra/llwindow/llwindowsdl2.cpp
cfc71a47db