sparc: soft-float support library

No sparc implementation actually has "long double" implemented in
hardware. The instructions are defined in the spec, but they are caught
and emulated by traps.

gcc even bypasses the traps and calls the support functions directly.

Import the required functions from FreeBSD (they implement the
operations as specified in the sparc ABI) and link them into the kernel,
for now (they will also need to be in libroot).

Change-Id: Ifc21faa29fffa4bf5d3941468b62d81229a44971
Reviewed-on: https://review.haiku-os.org/c/1137
Reviewed-by: waddlesplash <waddlesplash@gmail.com>