Use _spawnvp to replace fork for non-Unix platforms.

configure.ac

diff --git a/configure.ac b/configure.ac
index b505500..8eb46ee 100644
--- a/configure.ac
+++ b/configure.ac
@@ -946,6 +946,7 @@
 	_pclose \
 	_popen \
 	_snprintf \
+	_spawnvp \
 	_stricmp \
 	_strnicmp \
 	_vsnprintf \