libffi: upgrade 3.4.5 -> 3.4.6

libffi: upgrade 3.4.5 -> 3.4.6

meta/recipes-support/libffi/libffi/not-win32.patch
refreshed for 3.4.6

Changelog:
===========
-chore: update version to 3.4.6 and fix long double regression on mips64 and alpha
-Update sparc64 host
-Update cfarm hostnames
-Always define long double types
-update copyright year in libffi.texi
-Update version, copyright and testsuite info
-Fix test filename reference

Signed-off-by: Wang Mingyu <wangmy@fujitsu.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>