Move LLDB initialization/shutdown to Initialization.

Move LLDB initialization/shutdown to Initialization.

This creates a new top-level folder called Initialization which
is intended to hold code specific to LLDB system initialization.
Currently this holds the Initialize() and Terminate() functions,
as well as the fatal error handler.

This provides a means to break the massive dependency cycle which
is caused by the fact that Debugger depends on Initialize and
Terminate which then depends on the entire LLDB project.  With
this structure, it will be possible for applications to invoke
lldb_private::Initialize() directly, and have that invoke
Debugger::Initialize.

llvm-svn: 232768