Make some dynamic X11 symbols option. _XData32 and _XRead32 are only available on 64-bit systems, and are chosen with macros in the X11 headers. So on 32-bit systems, it should fail to find these symbols and keep going anyhow.

## Makefile.am for the AmigaOS joystick driver for SDL

noinst_LTLIBRARIES = libjoystick_amiga.la
libjoystick_amiga_la_SOURCES = $(SRCS)

# The SDL joystick driver sources
SRCS =  SDL_sysjoystick.c