More on autogen 5 build failure

[Richard Kenner]

    > opts.c: In function `doOptLoad_Functions':
    > opts.c:755: `RTLD_GLOBAL' undeclared (first use in this function)
    > opts.c:755: (Each undeclared identifier is reported only once
    > opts.c:755: for each function it appears in.)
    > 
    > And indeed I don't see that symbol defined anywhere in the autogen
    > package.

    That macro is defined when including <dlfcn.h> on my glibc2.2 based
    Linux system.

Well I'm on a Dec Unix ("Tru64").  It seems there's an autoconf test
missing.