Fix 'internal_equal' so that it uses at most one hash table

Fix 'internal_equal' so that it uses at most one hash table

The old implementation passed the hash table by value in
recursive tests, which would cause each recursive level to
initialize its own hash table, causing excess memory usage.
* src/fns.c (internal_equal): Delegate to 'internal_equal_1'.
(internal_equal_1): New function; body from old 'internal_equal'.
Pass the hash table argument by reference instead of by value.
(Bug#73883)

(cherry picked from commit 200214ca68f00722bf906bbf2a2afa81d139d5dc)