Make M*LIB stricter for INIT_MOVE operator:

* either the default INIT_MOVE operator works ('=')
* either an INIT_MOVE method is defined
* or it is disabled.
As a consequence, fix usage of testobj_t and mpz_t in the repository

The emulation layer of INIT_MOVE using INIT_SET+CLEAR is removed:
it wasn't working correctly with the local memory context
(INIT_MOVE doesn't need any local memory context to work,
 whereas INIT_SET/CLEAR does)
Remove macro M_DO_INIT_MOVE as it is now useless and uses M_CALL_INIT_MOVE.

The INIT_MOVE default method no longer sets the old 'src' to '0':
it was useless (it doesn't catch any error) and complicates compiler parsing.

Fix POD & A1 & CSTR & classic oplists definition (missing INIT_MOVE operators).

m-string.h

@@ -2357,6 +2357,7 @@ namespace m_lib {
    INIT_SET(M_F(name,_init_set)),                                             \
    SET(M_F(name,_set)),                                                       \
    CLEAR(M_F(name,_clear)),                                                   \
+   INIT_MOVE(M_COPY_A1_DEFAULT),                                              \
    NAME(name),                                                                \
    INIT_WITH( API_1(M_BOUNDED_STR1NG_INIT_WITH)),                             \
    HASH(M_F(name,_hash)),                                                     \