move "illegal anon sub" error from toke.c to perly.y

[mauke]

This fixes the TODO test in t/op/anonsub.t, but breaks two other tests:

• t/op/anonsub.t

    not ok 12 - '{ $x = sub }' is illegal
    # Failed test 12 - '{ $x = sub }' is illegal at t/op/anonsub.t line 15
    #      got 'Global symbol \"$x\" requires explicit package name (did you forget to declare \"my $x\"?) at (eval 12) line 1, <DATA> line 87.\nIllegal declaration of anonymous subroutine at (eval 12) line 1, at EOF\n'
    # expected /(?^:^Illegal declaration of anonymous subroutine at)/
  

• t/lib/croak.t

    FILE: lib/croak/toke ; line 644
    PROG:
    no feature 'apostrophe_as_package_separator';
    sub 'Hello'_he_said (_);
    EXPECTED:
    Illegal declaration of anonymous subroutine at - line 2.
    EXIT STATUS: != 0
    GOT:
    Bareword found where operator expected (Missing operator before "_he_said"?) at - line 2, near "'Hello'_he_said"
    Illegal declaration of anonymous subroutine at - line 2, near "sub 'Hello'"
    Execution of - aborted due to compilation errors.
    EXIT STATUS: 255
    not ok 247 - tick in names: initial character of sub name (no feature)
    # Failed test 247 - tick in names: initial character of sub name (no feature) at lib/croak/toke line 644
  

Since we don't immediately error out from the lexer anymore, the parser may accumulate more errors before failing with "Illegal declaration of anonymous subroutine".

See #5959.

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• This set of changes requires a perldelta entry, and it is included.
• This set of changes requires a perldelta entry, and I need help writing it.
• This set of changes does not require a perldelta entry.