add RTLD_DEEPBIND support to dlopen()
GNU libc 2.3.4 added RTLD_DEEPBIND:
Place the lookup scope of the symbols in this library ahead of the global scope. This means that a self-contained library will use its own symbols in preference to global symbols with the same name contained in libraries that have already been loaded. This flag is not specified in POSIX.1-2001.
Some new software (e.g. the latest cairo-dock) is using it now and it would be nice to have it in Illumos.