(export YYLTYPE): Don't invoke "cc a.c b.c -o c"; the HP-UX 11i C

compiler chatters during compilation.  Instead, invoke "cc -c a.c -o
a.o; cc -c b.c -o b.o; cc a.o b.o -o c".

tests/headers.at

@@ -123,7 +123,9 @@ main (void)
 
 # Link and execute, just to make sure everything is fine (and in
 # particular, that MY_LLOC is indeed defined somewhere).
-AT_COMPILE([caller], [caller.c input.c])
+AT_COMPILE([caller.o], [-c caller.c])
+AT_COMPILE([input.o], [-c input.c])
+AT_COMPILE([caller], [caller.o input.o])
 AT_PARSER_CHECK([./caller])
 
 AT_CLEANUP