Check for vsnprintf and _vsnprintf, and define vsnprintf with
_vsnprintf if needed.

diff --git a/configure b/configure
index f3cf658..7380226 100755
--- a/configure
+++ b/configure
@@ -13148,6 +13148,8 @@
 
 
 
+
+
 for ac_func in \
 	_lwp_create \
 	_pclose \
@@ -13155,6 +13157,7 @@
 	_snprintf \
 	_stricmp \
 	_strnicmp \
+	_vsnprintf \
 	chsize \
 	clone \
 	ecvt \
@@ -13202,6 +13205,7 @@
 	timegm \
 	usleep \
 	vfscanf \
+	vsnprintf \
 	wait4 \
 	waitpid \