Fix MSVC compile errors in pfpo.c

Add static keyword to internal subroutines
Fix error C2371: 'FLOAT' :  redefinition; different basic types
Fix warning C4101: 'class' : unreferenced local variable
Correct spelling mistake in comment
Set STFL bit 44

Certain operating systems (including Linux when the kernel
is compiled with MARCH=Z10) test for the presence of the
PFPO feature even though the PFPO instruction may not be
needed to run the control program or kernel. If the feature
is not indicated as present in the STFL feature bits then
Linux will stop after module head.S issues the message:
"The Linux kernel requires more recent processor hardware"
Other operating systems may enter a disabled wait state.
Setting STFL bit 44 will permit initialisation to continue
even though the PFPO instruction is not yet implemented.