Move assert for av_new_alloc() to embed.fnc

You can't allocate a zero length array using this function; this uses
the new assert() functionality in embed.fnc introduced in the previous
few commits to cause the assertion to be placed in
PERL_ARGS_ASSERT_AV_NEW_ALLOC rather than be in the function.

There is no particular need to do this; this is mostly a demonstration
of how it can be done.

Author: khwilliamson

embed.fnc

@@ -747,7 +747,8 @@ ARdp	|SSize_t|av_len 	|NN AV *av
 ARdp	|AV *	|av_make	|SSize_t size				\
 				|NN SV **strp
 CRdip	|AV *	|av_new_alloc	|SSize_t size				\
-				|bool zeroflag
+				|bool zeroflag				\
+				assert(size > 0)
 p	|SV *	|av_nonelem	|NN AV *av				\
 				|SSize_t ix
 Adp	|SV *	|av_pop 	|NN AV *av

inline.h

@@ -195,10 +195,10 @@ initialized.
 PERL_STATIC_INLINE AV *
 Perl_av_new_alloc(pTHX_ SSize_t size, bool zeroflag)
 {
+    PERL_ARGS_ASSERT_AV_NEW_ALLOC;
+
     AV * const av = newAV();
     SV** ary;
-    PERL_ARGS_ASSERT_AV_NEW_ALLOC;
-    assert(size > 0);
 
     Newx(ary, size, SV*); /* Newx performs the memwrap check */
     AvALLOC(av) = ary;