libc: fork() failed when using dlopen()

[froloff]

If process load module dynamically (dlopen) after that fork will fail.

I examine the situation a bit and divide it into 3 cases

1. process dlopen() module then forking. Child process failed during initial fork processing.
2. process dlopen() module, dlclose() module then forking. Parent process trapped during fork processing.
3. process dlopen() module, dlclose() module, dlopen() module again then forking. Parent process goes endless loop in forkParValidateModules() during fork processing.

I'll send testcase and libc logs via email.

Note. I didn't find code deregistering module from modules chain - conj procedure to __libc_ForkRegisterModule().