Round a mpq_t number to the nearest integer

[behnaz.bostanipour at epfl.ch]

Hello;
I have a number "a" of type mpq_t and I would like
to round it to the nearest integer.The result can be
of type mpz_t or another type.Is there any function
which can help me to do so or should I implement it
myself?
Thanks,
RGDS,
B.