* configure.in: Pass "-Isrc" to the CPP we run to examine the

s/*.h and m/*.h files.  Martin Tomes
	<mt00@controls.eurotherm.co.uk> says ISC Unix 3.0.1 needs it.

configure1.in

@@ -1110,7 +1110,7 @@ echo '
 # The value of CPP is a quoted variable reference, so we need to do this
 # to get its actual value...
 foo=`eval "echo $CPP"`
-eval `${foo} ${tempcname} \
+eval `${foo} -Isrc ${tempcname} \
        | grep '@configure@' \
        | sed -e 's/^@configure@ \([^=]*=\)\(.*\)$/\1"\2"/'`
 rm ${tempcname}