Dear all,

the attached obvious patch fixes a memory leak with gmp variables
that are set but apparently (=valgrind) never cleared.  No new
testcase as the current testsuite gives enough coverage
(confirmed by trying a faulty version...) and as per discussion
with Steve (see PR).

Committed after regtesting on x86_64-pc-linux-gnu as:
r13-5095-gfec9fc1a17ec44461cee841513f1b6b8ad680fe4

Thanks,
Harald