If we have a symbol which has a different definition depending on a c
pre-processor condition, include the condition when de-duping.

For instance if in intrpvar.h we had

    #ifdef HAS_QUAD
    PERLVAR(I, SomeField, U64TYPE)
    #else
    PERLVAR(I, SomeField, U32)
    #endif

We don't want to throw warnings about duplicate SomeField, as only one
of the definitions will be active at a time.

This includes changes to regen/HeaderParser.pl to facilitate this, by
adding a cond_as_str() method to the HeaderLine objects.

I am not sure what we should do with the internal_random_state in
perl_clone() but it should either be treated the same as random_state or
it should be independently intialized somehow. We shouldn't leave the
states content undefined.

This makes it so that the internal RNG support functions
and variables are named the same as their non-internal
equivalents, but with _internal as a suffix. This should
make it easier to find them. For instance PL_internal_random_state
will not show up when searching for PL_random_state, but
PL_random_state_internal will.

Same for &PL_random_state_internal, which gets replaced with
PL_PTR_RANDOM_STATE_INTERNAL.

We also create a similar define for &(proto_perl->Irandom_state)
which gets replaced by PL_PTR_PROTO_RANDOM_STATE, and
&(proto_perl->Irandom_state_internal) which gets replaced by
PL_PTR_PROTO_RANDOM_STATE_INTERNAL.

We provide our own RNG, we do not need any information from Configure
about the system RNG. Configure basically should not be involved in such
things, just like it isn't with regard to hash functions.

This is a placeholder commit so that Tux knows what need to be done and
for discussion purposes. It isn't intended for direct merging. The
change needs to be done the normal way for Configure changes.