StdLib/LibC: Add software floating point library from NetBSD

StdLib/LibC: Add software floating point library from NetBSD

Floating point processing is not supported on ARM for UEFI. In order to
support UEFI applications in AppPkg we use this library to provide the
required functionality.

Changes as compared to the NetBSD version:
- Formatting changes (tabs to spaces, DOS line endings etc).
- Disable exceptions as described in the float_raise() function.
- Disable definition of 'Symbolic Boolean literals' in milieu.h.

Source originally from: NetBSD project
- Source: http://cvsweb.netbsd.org/bsdweb.cgi/?only_with_tag=MAIN
- Licensing and Copyright: http://www.netbsd.org/about/redistribution.html

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Harry Liebel <Harry.Liebel@arm.com>
Reviewed-by: Olivier Martin <Olivier.Martin@arm.com>
Reviewed-by: Daryl McDaniel <edk2-lists@mc2research.org>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18116 6f19259b-4bc3-4df7-8a09-765794883524