Fix push/pop mismatch

Without this, perlhead.swg does `#pragma GCC diagnostic pop`
if `__GNUC__ >= 10` - without any prior `#pragma GCC diagnostic push`.

There's also a mismatch between the conditions that trigger
`#pragma GCC diagnostic ignored` (where the `push` should be)
and the attempt to `#pragma GCC diagnostic pop`.

Author: berolinux

CHANGES.current

@@ -7,6 +7,9 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.1.1 (30 Nov 2022)
 ===========================
 
+2022-11-29: bero
+            Fix mismatch between #pragma GCC diagnostic push and pop statements
+
 2022-11-26: wsfulton
             #2449 Fix undefined behaviour in ccache-swig calculating md4 hashes and possibly
             also handling errors when CCACHE_CPP2 is set.

Lib/perl5/perlhead.swg

@@ -7,6 +7,7 @@ extern "C" {
 
 #if __GNUC__ >= 10
 #if defined(__cplusplus)
+#pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wvolatile"
 #endif
 #endif
@@ -16,8 +17,10 @@ extern "C" {
 #include "XSUB.h"
 
 #if __GNUC__ >= 10
+#if defined(__cplusplus)
 #pragma GCC diagnostic pop
 #endif
+#endif
 
 /* PERL_REVISION was added in Perl 5.6. */
 #if !defined PERL_REVISION || (PERL_REVISION-0 == 5 && PERL_VERSION-0 < 8)