C 1.49_01: fix DBI #359

special case DBI_MAGIC methods,
add an extra call to DBI->_install_method to re-initialize compile-time
internal ima pointers. ('~' DBI_MAGIC)

also store XSUBANY.any_long and use a heuristic to skip storing
compile-time pointers. storing ptrs broke Tie::Hash::NamedCapture (90)
also add example t/pg.pl: DBI_TRACE=0 t/pg