Avoid implicit function declarations for increased C99 compatibility.

The PCRE POSIX interfaces are actually in <pcreposix.h>, not <pcre.h>
these days.  Without <pcreposix.h>, you link against the glibc
implementation.

diff -ur kdelibs-3.5.10.orig/admin/libtool.m4.in kdelibs-3.5.10/admin/libtool.m4.in
--- kdelibs-3.5.10.orig/admin/libtool.m4.in	2022-12-13 18:41:33.019971275 +0100
+++ kdelibs-3.5.10/admin/libtool.m4.in	2022-12-13 18:49:43.008763735 +0100
@@ -760,10 +760,6 @@
 #  endif
 #endif
 
-#ifdef __cplusplus
-extern "C" void exit (int);
-#endif
-
 void fnord() { int i=42;}
 int main ()
 {
@@ -777,7 +773,7 @@
       /* dlclose (self); */
     }
 
-    exit (status);
+    return status;
 }]
 EOF
   if AC_TRY_EVAL(ac_link) && test -s conftest${ac_exeext} 2>/dev/null; then
diff -ur kdelibs-3.5.10.orig/kdecore/fakes.c kdelibs-3.5.10/kdecore/fakes.c
--- kdelibs-3.5.10.orig/kdecore/fakes.c	2006-07-22 10:16:41.000000000 +0200
+++ kdelibs-3.5.10/kdecore/fakes.c	2022-12-13 19:10:28.504547863 +0100
@@ -22,6 +22,7 @@
 #include "kdelibs_export.h"
 
 #include <config.h>
+#include <string.h>
 
 #ifdef _WIN32
 #include <kde_file_win.h>
@@ -38,7 +39,6 @@
 #include <alloca.h>
 #endif
 
-#include <string.h>
 #include <stdlib.h>
 #include <unistd.h>
 
diff -ur kdelibs-3.5.10.orig/kinit/start_kdeinit.c kdelibs-3.5.10/kinit/start_kdeinit.c
--- kdelibs-3.5.10.orig/kinit/start_kdeinit.c	2008-08-19 20:18:12.000000000 +0200
+++ kdelibs-3.5.10/kinit/start_kdeinit.c	2022-12-13 19:30:22.674120114 +0100
@@ -25,6 +25,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/stat.h>
 #include <unistd.h>
 
 #ifdef KDEINIT_OOM_PROTECT
diff -ur kdelibs-3.5.10.orig/kio/misc/kpac/configure.in.in kdelibs-3.5.10/kio/misc/kpac/configure.in.in
--- kdelibs-3.5.10.orig/kio/misc/kpac/configure.in.in	2005-09-10 10:26:47.000000000 +0200
+++ kdelibs-3.5.10/kio/misc/kpac/configure.in.in	2022-12-13 19:11:41.002789619 +0100
@@ -3,6 +3,9 @@
 AC_MSG_CHECKING([for setgroups with short argument])
 AC_CACHE_VAL([kde_cv_shortsetgroups],[
     AC_TRY_RUN([
+	#include <grp.h>
+	#include <stdlib.h>
+	#include <unistd.h>
         int main()
         {
             short x[4];
diff -ur kdelibs-3.5.10.orig/kjs/configure.in.in kdelibs-3.5.10/kjs/configure.in.in
--- kdelibs-3.5.10.orig/kjs/configure.in.in	2007-10-08 11:52:09.000000000 +0200
+++ kdelibs-3.5.10/kjs/configure.in.in	2022-12-13 19:00:51.627479229 +0100
@@ -66,7 +66,7 @@
       ac_LDFLAGS_save="$LDFLAGS"
       LDFLAGS="$LDFLAGS $all_libraries"
       AC_TRY_LINK(
-         [#include <pcre.h>],
+         [#include <pcreposix.h>],
          [regfree(0);],
          [ac_cv_have_pcreposix="yes"],
          [ac_cv_have_pcreposix="no"]