Fix memory leak introduced by !15

assigned to @vifley

mentioned in issue picodata/picodata/tarantool-module#111

closed

The following commits were cherry-picked from upstream/master to reimplement memory management for stored C procedures and solve the problem that !15 (merged) tried to solve (this time - no memory leaks). And !15 (merged) was dropped.

feb2e623 25ee1510 05be796c e8574eb5 e2b8d9da 31502b92

mentioned in merge request !223 (merged)