trimcore/0 reclaims space in all of Prolog's data areas. At any
given time, each data area contains some free space. For example, the
local stack space contains the local stack and some free space for
that stack to grow into. The data area is automatically expanded when
it runs out of free space, and it remains expanded until
trimcore/0 is called, even though the stack may have shrunk
considerably in the meantime. The effect of trimcore/0 is to
reduce the free space in all the data areas as much as possible, and to
give the space no longer needed back to the operating system.
trimcore/0 is called each time Prolog returns to the
top level or the top of a break level.