Devel::PPPort: add compatibility entries for the new vstrings

Based on @leont's comment on #23160.

This seems to produce reasonable results:

tony@venus:.../git/perl6$ cat foo.c
SvVSTRING
tony@venus:.../git/perl6$ ./perl -Ilib dist/Devel-PPPort/ppport.h --nofilter foo.c
Scanning foo.c ...
=== Analyzing foo.c ===
Uses SvVSTRING, which depends on sv_vstring_get, SvVSTRING_mg, mg_find, PERL_MAGIC_vstring, SvMAGICAL
File needs sv_vstring_get, adding static request
Needs to include 'ppport.h'
Analysis completed
Suggested changes:
--- foo.c       2025-04-01 10:51:39.040415623 +1100
+++ foo.c.patched       2025-04-01 10:55:11.347014468 +1100
@@ -1 +1,3 @@
+#define NEED_sv_vstring_get
+#include "ppport.h"
 SvVSTRING

MANIFEST

@@ -3838,6 +3838,7 @@ dist/Devel-PPPort/parts/base/5035007
 dist/Devel-PPPort/parts/base/5035008
 dist/Devel-PPPort/parts/base/5035009
 dist/Devel-PPPort/parts/base/5035010
+dist/Devel-PPPort/parts/base/5041010
 dist/Devel-PPPort/parts/embed.fnc		Devel::PPPort Perl API listing
 dist/Devel-PPPort/parts/inc/01_test		Devel::PPPort include
 dist/Devel-PPPort/parts/inc/call		Devel::PPPort include
@@ -4112,6 +4113,7 @@ dist/Devel-PPPort/parts/todo/5035007
 dist/Devel-PPPort/parts/todo/5035008
 dist/Devel-PPPort/parts/todo/5035009
 dist/Devel-PPPort/parts/todo/5035010
+dist/Devel-PPPort/parts/todo/5041010
 dist/Devel-PPPort/PPPort.xs			Devel::PPPort dummy PPPort.xs
 dist/Devel-PPPort/ppport_h.PL			Devel::PPPort ppport.h writer
 dist/Devel-PPPort/PPPort_pm.PL			Devel::PPPort PPPort.pm writer

dist/Devel-PPPort/parts/base/5041010

@@ -0,0 +1,2 @@
+5.041010
+sv_vstring_get                 # U

dist/Devel-PPPort/parts/todo/5041010

@@ -0,0 +1,2 @@
+5.041010
+