Deparse.pm:pp_entereval: Redundant func call

unop calls $self->keyword, so we don’t need to.
Deparse require(foo()) correctly

require(foo()) deparses as require foo().  But require’s parsing is
eccentric, and does not allow require foo(), because ‘foo’ is treated
as a bareword there, and ‘require WORD’ does not allow () fol-
lowing it.

The same problem happens with do-file, which is fixed also by this
commit, since it follows the same code path.
Deparse goto foo() correctly

See the previous commit.  The same applies to loop controls and similar
keywords.
Tweak Deparse-core.t after the last two commits