fix killpg on Win32, to meet posix expectations for killpg

On Win32 Perls built without PERL_IMPLICIT_SYS, killpg from win32.c was
directly called by Perl_apply, yet killpg's return value had Win32
behavior, not POSIX behavior. Modify killpg token to have same meaning as
PerlProcKillpg/PerlProc_killpg has on PERL_IMPLICIT_SYS builds. Use a
macro rather than create a win32_killpg C function since win32_killpg would
be nothing but a call to win32_kill anyways. win32_kill contains the Win32
to POSIX semantics conversion code. Rename old killpg to my_killpg since
it has no use outside of win32.c. The psuedo-PID code in win32_kill also
played a factor in not writing a separate win32_killpg that calls
my_killpg. This fix is tested by kill0.t passing on
no-PERL_IMPLICIT_SYS builds.

[perl #121230]

Author: bulk88

pod/perldelta.pod

@@ -316,6 +316,14 @@ a bug in which the timeout monitor used for tests could not be cancelled once
 the test completes, and the full timeout period elapsed before running the next
 test file.
 
+On a Perl built without psuedo-fork (psuedo-fork builds were not affected by
+this bug), probably since prcess tree kill feature was implemented on Win32,
+killing a process tree with L<perlfunc/kill> and a negative signal, resulted
+in kill inverting the returned value.  This ment successfully killing
+1 process tree PID returned 0, and also passing 2 invalid PID, returned 2.
+This has been corrected so the documented behavior for return values for kill
+executes.  [perl #121230]
+
 =back
 
 =head1 Internal Changes

win32/win32.c

@@ -139,6 +139,7 @@ static int	do_spawnvp_handles(int mode, const char *cmdname,
 static long	find_pid(pTHX_ int pid);
 static void	remove_dead_process(long child);
 static int	terminate_process(DWORD pid, HANDLE process_handle, int sig);
+static int	my_killpg(int pid, int sig);
 static int	my_kill(int pid, int sig);
 static void	out_of_memory(void);
 static char*	wstr_to_str(const wchar_t* wstr);
@@ -1250,8 +1251,9 @@ terminate_process(DWORD pid, HANDLE process_handle, int sig)
     return 0;
 }
 
-int
-killpg(int pid, int sig)
+/* returns number of processes killed */
+static int
+my_killpg(int pid, int sig)
 {
     HANDLE process_handle;
     HANDLE snapshot_handle;
@@ -1271,7 +1273,7 @@ killpg(int pid, int sig)
         if (Process32First(snapshot_handle, &entry)) {
             do {
                 if (entry.th32ParentProcessID == (DWORD)pid)
-                    killed += killpg(entry.th32ProcessID, sig);
+                    killed += my_killpg(entry.th32ProcessID, sig);
                 entry.dwSize = sizeof(entry);
             }
             while (Process32Next(snapshot_handle, &entry));
@@ -1282,14 +1284,15 @@ killpg(int pid, int sig)
     return killed;
 }
 
+/* returns number of processes killed */
 static int
 my_kill(int pid, int sig)
 {
     int retval = 0;
     HANDLE process_handle;
 
     if (sig < 0)
-        return killpg(pid, -sig);
+        return my_killpg(pid, -sig);
 
     process_handle = OpenProcess(PROCESS_TERMINATE, FALSE, pid);
     /* OpenProcess() returns NULL on error, *not* INVALID_HANDLE_VALUE */

win32/win32.h

@@ -322,7 +322,6 @@ extern  gid_t	getegid(void);
 extern  int	setuid(uid_t uid);
 extern  int	setgid(gid_t gid);
 extern  int	kill(int pid, int sig);
-extern  int	killpg(int pid, int sig);
 #ifndef USE_PERL_SBRK
 extern  void	*sbrk(ptrdiff_t need);
 #  define HAS_SBRK_PROTO

win32/win32iop.h

@@ -448,6 +448,11 @@ END_EXTERN_C
 #  undef kill
 #endif
 #define kill			win32_kill
+#ifdef UNDER_CE
+#  undef killpg
+#endif
+#define killpg(pid, sig)	win32_kill(pid, -(sig))
+
 
 #ifdef UNDER_CE
 #  undef opendir