Followup on a4570f51 for t/porting/extrefs.t

Followup on a4570f51 for t/porting/extrefs.t

More functions have appeared that are PERL_STATIC_INLINE, but the
porting/extrefs.t compiles with -DPERL_NO_INLINE_FUNCTIONS, which
means no bodies are visible, but the Tru64 cc takes static inline
seriously, requiring the bodies.

Instead of the manual tweak of adding #ifndef PERL_NO_INLINE_FUNCTIONS
to embed.fnc, fix the problem in embed.pl so that 'i' type inserts the
required ifndef.  Remove the manual PERL_NO_INLINE_FUNCTIONS insertions
made in a4570f51 (note that the types of some have diverged).
Now the extrefs.t again works in Tru64 (and no other compiler
has ever tripped on this).