don't segfault on blead [#83439]

Turns out newATTRSUB can return NULL for subs with parse errors since
commit 9ffcdca1f504cb09088413c074b35af4b7f247e3. Handle that case.
don't double-free OPs on blead [#83439]

Starting with 5.17.2 all newly allocated OPs are implicitly registered
with the current CV being compiled (PL_compcv). If an error is thrown
during compilation, these OPs are freed with the CV. This results in a
double-free if we also track and free OPs ourselves.

Solution: Check for this case and don't call op_free() in this
situation.
multitest more perl versions; also list successes
replace deprecated is_utf8_xidfirst/cont by isIDFIRST_uni/isALNUM_uni
version bump (developer release)