initdb needs pqsignal() even on Windows.

I had thought we weren't using this version of pqsignal() at all on
Windows, but that's wrong --- initdb is using it (and coping with the
POSIX-ish semantics of bare signal() :-().  So allow the file to be
built in WIN32+FRONTEND case, and add it to the MSVC build logic.

src/include/port.h

@@ -463,11 +463,8 @@ extern int	pg_check_dir(const char *dir);
 extern int	pg_mkdir_p(char *path, int omode);
 
 /* port/pqsignal.c */
-/* On Windows, we can emulate pqsignal in the backend, but not frontend */
-#if !defined(WIN32) || !defined(FRONTEND)
 typedef void (*pqsigfunc) (int signo);
 extern pqsigfunc pqsignal(int signo, pqsigfunc func);
-#endif
 
 /* port/quotes.c */
 extern char *escape_single_quotes_ascii(const char *src);

src/port/pqsignal.c

@@ -29,10 +29,12 @@
  *	neither POSIX signals nor BSD signals.	The alternative is to do
  *	signal-handler reinstallation, which doesn't work well at all.
  *
- *	Windows, of course, is resolutely in a class by itself.  This file
- *	should not get compiled at all on Windows.  We have an emulation of
- *	pqsignal() in src/backend/port/win32/signal.c for the backend
- *	environment; frontend programs are out of luck.
+ *	Windows, of course, is resolutely in a class by itself.  In the backend,
+ *	we don't use this file at all; src/backend/port/win32/signal.c provides
+ *	pqsignal() for the backend environment.  Frontend programs can use
+ *	this version of pqsignal() if they wish, but beware that Windows
+ *	requires signal-handler reinstallation, because indeed it provides
+ *	neither POSIX signals nor BSD signals :-(
  * ------------------------------------------------------------------------
  */
 
@@ -40,14 +42,12 @@
 
 #include <signal.h>
 
-#ifndef WIN32
+#if !defined(WIN32) || defined(FRONTEND)
 
 /*
  * Set up a signal handler for signal "signo"
  *
- * Returns the previous handler.  It's expected that the installed handler
- * will persist across multiple deliveries of the signal (unlike the original
- * POSIX definition of signal(2)).
+ * Returns the previous handler.
  */
 pqsigfunc
 pqsignal(int signo, pqsigfunc func)
@@ -73,4 +73,4 @@ pqsignal(int signo, pqsigfunc func)
 #endif   /* !HAVE_POSIX_SIGNALS */
 }
 
-#endif /* WIN32 */
+#endif /* !defined(WIN32) || defined(FRONTEND) */

src/tools/msvc/Mkvcbuild.pm

@@ -69,7 +69,8 @@ sub mkvcbuild
 	  chklocale.c crypt.c fls.c fseeko.c getrusage.c inet_aton.c random.c
 	  srandom.c getaddrinfo.c gettimeofday.c inet_net_ntop.c kill.c open.c
 	  erand48.c snprintf.c strlcat.c strlcpy.c dirmod.c exec.c noblock.c path.c
-	  pgcheckdir.c pg_crc.c pgmkdirp.c pgsleep.c pgstrcasecmp.c qsort.c qsort_arg.c quotes.c
+	  pgcheckdir.c pg_crc.c pgmkdirp.c pgsleep.c pgstrcasecmp.c pqsignal.c
+	  qsort.c qsort_arg.c quotes.c
 	  sprompt.c tar.c thread.c wait_error.c getopt.c getopt_long.c dirent.c rint.c win32env.c
 	  win32error.c win32setlocale.c);