Previously, the isc_mem_create() and isc_mem_createx() functions took `max_size`
and `target_size` as first two arguments.  Those values were never used in the
BIND 9 code.  The refactoring removes those arguments and let BIND 9 always use
the default values.

Previously, the isc_mem_create() and isc_mem_createx() functions could have
failed because of failed memory allocation.  As this was no longer true and the
functions have always returned ISC_R_SUCCESS, the have been refactored to return
void.