configure: Don't use a default soname if a library is not found, leave it undefined.
[wine] / programs / explorer /
drwxr-xr-x   ..
-rw-r--r-- 440 Makefile.in
-rw-r--r-- 6647 desktop.c
-rw-r--r-- 7627 device.c
-rw-r--r-- 4631 diskarb.c
-rw-r--r-- 5299 explorer.c
-rw-r--r-- 1277 explorer_private.h
-rw-r--r-- 7177 hal.c
-rw-r--r-- 14170 systray.c