Added a new header file: SDL_loadso.h It contains the following functions: SDL_LoadObject(), SDL_LoadFunction(), SDL_UnloadObject() The UNIX esd and arts audio code use these to dynamically load their respective audio libraries.

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

noinst_LTLIBRARIES = libjoystick_macos.la
libjoystick_macos_la_SOURCES = $(SRCS)

# The SDL joystick driver sources
SRCS =  SDL_sysjoystick.c