[test] fix extend_vtable.t for changed rpa delete API

delete throws now out of bounds.
Also enable TEST_VERBOSE=2 for c_output tests
[pmc] rpa: just aesthetics
[pmc] rpa.delete warn on illegal delete[0] of empty array

it skipped the memmove, so did no harm. But PGE still uses that, so keep the warning
for one deprecation cycle. Closes GH #1153
[pmc] rpa.delete: skip memmove when not needed

also adjust changed out of bounds error message in one test