Prevent Okular from crashing when synctex logs an error

bd20e48c3c updated Okular's copy of the synctex code to 1.19.
Unfortunately since this version the upstream code logs errors like
`"! SyncTeX Error : Ignored record...` when accessing selected synctex
files created with older versions of synctex.

The upstream `_synctex_log` contains `va_list arg` as a parameter, but
fails to initialize and tear down this properly via `va_start` and
`va_end`. In general this seems to work for the single argument case.
However, once we apply our hardening patch to get rid of the
`gnu_printf format attribute` warning and thus introduce a variadic
argument, things go wrong.

To fix this, we add the missing code. The remaining changes are just
refreshing the patches.

BUG: 383915

Test Plan:
Opening `empty.pdf` with `empty.synctex.gz` from
https://bugs.kde.org/attachment.cgi?id=109116 located
in the same folder does not lead to Okular segfaulting anymore.

core/synctex/patches/04-gcc-specify-printf-format.diff

@@ -54,7 +54,7 @@ Index: synctex/synctex_parser_utils.c
 ===================================================================
 --- synctex.orig/synctex_parser_utils.c
 +++ synctex/synctex_parser_utils.c
-@@ -87,7 +87,9 @@ void _synctex_free(void * ptr) {
+@@ -87,8 +87,11 @@ void _synctex_free(void * ptr) {
  #   include <syslog.h>
  #endif
  
@@ -63,5 +63,15 @@ Index: synctex/synctex_parser_utils.c
 +int _synctex_log(int level, const char * prompt, const char * reason, ...) {
 +    va_list arg;
  	int result;
++    va_start(arg, reason);
  #	ifdef SYNCTEX_RECENT_WINDOWS
  	{/*	This code is contributed by William Blum.
+         As it does not work on some older computers,
+@@ -130,6 +133,7 @@ int _synctex_log(int level, const char *
+     result += vfprintf(where, reason, arg);
+     result += fprintf(where,"\n");
+ #   endif
++    va_end(arg);
+ 	return result;
+ }
+ 

core/synctex/patches/06-mingw-_synctex_error.diff

@@ -7,7 +7,7 @@ Index: synctex/synctex_parser_utils.c
 ===================================================================
 --- synctex.orig/synctex_parser_utils.c
 +++ synctex/synctex_parser_utils.c
-@@ -103,8 +103,26 @@ int _synctex_log(int level, const char *
+@@ -104,8 +104,26 @@ int _synctex_log(int level, const char *
  		char *buff;
  		size_t len;
  		OutputDebugStringA(prompt);

core/synctex/patches/08-fix_cpp_comments.diff

@@ -27,7 +27,7 @@ Index: synctex/synctex_parser_utils.c
 ===================================================================
 --- synctex.orig/synctex_parser_utils.c
 +++ synctex/synctex_parser_utils.c
-@@ -585,6 +585,6 @@ int _synctex_get_name(const char * outpu
+@@ -587,6 +587,6 @@ int _synctex_get_name(const char * outpu
  
  const char * _synctex_get_io_mode_name(synctex_io_mode_t io_mode) {
      static const char * synctex_io_modes[4] = {"r","rb","a","ab"}; 

core/synctex/patches/10-fix-typo.diff

@@ -6,7 +6,7 @@ Index: synctex/synctex_parser_utils.c
 ===================================================================
 --- synctex.orig/synctex_parser_utils.c
 +++ synctex/synctex_parser_utils.c
-@@ -408,7 +408,7 @@ char * _synctex_merge_strings(const char
+@@ -410,7 +410,7 @@ char * _synctex_merge_strings(const char
  
  /*  The purpose of _synctex_get_name is to find the name of the synctex file.
   *  There is a list of possible filenames from which we return the most recent one and try to remove all the others.

core/synctex/patches/13-fix-Wundef-warnings.diff

@@ -315,7 +315,7 @@ Index: synctex/synctex_parser_utils.c
 ===================================================================
 --- synctex.orig/synctex_parser_utils.c
 +++ synctex/synctex_parser_utils.c
-@@ -128,7 +128,7 @@ int _synctex_log(int level, const char *
+@@ -129,7 +129,7 @@ int _synctex_log(int level, const char *
  		OutputDebugStringA("\n");
  		free(buff);
  	}

core/synctex/synctex_parser_utils.c

@@ -91,6 +91,7 @@ int _synctex_log(int level, const char * prompt, const char * reason, ...) SYNCT
 int _synctex_log(int level, const char * prompt, const char * reason, ...) {
     va_list arg;
 	int result;
+    va_start(arg, reason);
 #	ifdef SYNCTEX_RECENT_WINDOWS
 	{/*	This code is contributed by William Blum.
         As it does not work on some older computers,
@@ -150,6 +151,7 @@ int _synctex_log(int level, const char * prompt, const char * reason, ...) {
     result += vfprintf(where, reason, arg);
     result += fprintf(where,"\n");
 #   endif
+    va_end(arg);
 	return result;
 }