patch for threads/76690 - critical - fork hang in child for -lc_r

[David Xu]

4.x does not have a __malloc_lock symbol exported,  I had suggested
to add __malloc_lock in FreeBSD 5 libpthread since I saw some broken
applications call malloc in child process after fork() and before 
execv(). :)

Julian Elischer wrote:

> the bug is still valid in 4.x
>
>
> Andriy Tkachuk wrote:
>
>>> Is there a reason you are still using libc_r?
>>>   
>>
>>
>> I don't use it at all, but there was critical bug
>> i threads-pr - so i just decided to fix it since i
>> have had some time )
>>
>> If this library is needless, why is it still there
>> and this pr in criticals? 
>