Support "--without-pgsql" (reported by Alex Songe via IRC).

git-svn-id: https://nagiosplug.svn.sourceforge.net/svnroot/nagiosplug/nagiosplug/trunk@1987 f882894a-f735-0410-b71e-b25c423dba1c

configure.in

@@ -181,7 +181,7 @@ AC_ARG_WITH(pgsql,
 		[sets path to pgsql installation]),
 	PGSQL=$withval,)
 AC_CHECK_LIB(crypt,main)
-if test "$ac_cv_lib_crypt_main" = "yes"; then
+if test "$ac_cv_lib_crypt_main" = "yes" -a "x$PGSQL" != "xno"; then
   if test -n "$PGSQL"; then
     LDFLAGS="$LDFLAGS -L$PGSQL/lib"
     CPPFLAGS="$CPPFLAGS -I$PGSQL/include"