Index: configure.in
===================================================================
--- configure.in	(revision 559)
+++ configure.in	(working copy)
@@ -568,6 +568,8 @@
 
 AC_CHECK_HEADERS(errno.h)
 
+AC_CHECK_HEADERS(unistd.h)
+
 # checking for a posix version of getpwnam_r
 # if we are cross compiling and can not run the test
 # assume getpwnam_r is the posix version