Add a TestFloat based test suite for floating-point implementations

Add a TestFloat based test suite for floating-point implementations
currently supporting sparc64. After a `make depend all` there are
three programs; testsoftfloat for testing against the SoftFloat in
src/lib/libc/softfloat for reference purposes, testemufloat for
testing the emulator source in src/lib/libc/sparc64/fpu and testfloat
for testing with the installed libc. Support for other architectures
can be added as needed.

PR:		144900
Submitted by:	Peter Jeremy