drop obsolete HAVE_DIX_CONFIG_H
The symbol controls whether to include dix-config.h, and it's always set, thus we don't need it (and dozens of ifdef's) anymore.
This commit only removes them from our own source files, where we can guarantee that dix-config.h is present - leaving the (potentially exported) headers untouched.
Edited by Enrico Weigelt, metux IT consult .