This patch is updating soft-fp from glibc:
1. Add __extendhfxf2 to return an IEEE half converted to IEEE extended.
2. Add __truncxfhf2 to truncate IEEE extended into IEEE half.
These are needed by x86 _Float16 support.
* soft-fp/extendhfxf2.c: New file.
* soft-fp/truncxfhf2.c: Likewise.
