Fix omissions in snprintf.c's coverage of standard *printf functions.

A warning on a NetBSD box revealed to me that pg_waldump/compat.c
is using vprintf(), which snprintf.c did not provide coverage for.
This is not good if we want to have uniform *printf behavior, and
it's pretty silly to omit when it's a one-line function.

I also noted that snprintf.c has pg_vsprintf() but for some reason
it was not exposed to the outside world, creating another way in
which code might accidentally invoke the platform *printf family.

Let's just make sure that we replace all eight of the POSIX-standard
printf family.

Also, upgrade plperl.h and plpython.h to make sure that they do
their undefine/redefine rain dance for all eight, not some random
maybe-sufficient subset thereof.

src/port/snprintf.c

@@ -102,9 +102,11 @@
 /* Prevent recursion */
 #undef	vsnprintf
 #undef	snprintf
+#undef	vsprintf
 #undef	sprintf
 #undef	vfprintf
 #undef	fprintf
+#undef	vprintf
 #undef	printf
 
 /*
@@ -208,7 +210,7 @@ pg_snprintf(char *str, size_t count, const char *fmt,...)
 	return len;
 }
 
-static int
+int
 pg_vsprintf(char *str, const char *fmt, va_list args)
 {
 	PrintfTarget target;
@@ -270,6 +272,12 @@ pg_fprintf(FILE *stream, const char *fmt,...)
 	return len;
 }
 
+int
+pg_vprintf(const char *fmt, va_list args)
+{
+	return pg_vfprintf(stdout, fmt, args);
+}
+
 int
 pg_printf(const char *fmt,...)
 {