Add the github action bot to build with cfi
Also fix all the known issues which require the change from C style cast to
static_cast inside the i18n and common directory while we are sure about
the object. and use
C++ style dynamic_cast for base-to-derive cast in other code inside i18n
and common and in test code or tool.
Change to use const_cast for casting between const / non-const
This is the normal standard way in C, C++ as well as Java and there's no
longer any reason for ICU to be different. The various internal macros
providing custom boolean constants can all be deleted and code as well
as documentation can be updated to use lowercase true/false everywhere.
Fix broken RTTI on Windows by splitting service registration into separate files,
and rename files for consistency at the request from Doug.
X-SVN-Rev: 16979