RFR: JDK-8026888: Licensee build failure due to wrong libs being called

[Erik Joelsson]

This patch removes the last reference to OPENWIN on linux. All other 
libs were already converted to using X_LIBS and X_CFLAGS instead of 
OPENWIN_HOME on linux, but libsplashscreen was still using OPENWIN. I 
also removed the logic in configure that probed for it.

Bug: https://bugs.openjdk.java.net/browse/JDK-8026888
Webrev: http://cr.openjdk.java.net/~erikj/8026888/webrev.01/

/Erik