making gnutls depended to pthread

[Nikos Mavrogiannopoulos]

Hello,
 I've been thinking it for quite some time but given the bug report:
https://savannah.gnu.org/support/?107409 , I think it might be relevant.
GnuTLS due to its use of random numbers will always need a global pool
to be accessed, and thus locking is mandatory. How about making a new
gnutls_global_init2() that accept flags such as USE_SYSTEM_LOCKS (that
would be pthread for linux), by default? This way gnutls will initialize
all libraries that it is depended on using the default threads for each
system.

regards,
Nikos