Summary:
Previously, there were two variants of CLOSURE in C--:

    - Top-level CLOSURE(foo_closure, foo, lits...), which defines a new
      static closure and gives it a name, and

    - Array CLOSURE(foo, lits...), which was used for the static char
      and integer arrays.

They used the same name, were confusing, and didn't even generate
the correct internal label representation!  So now, we have two
new forms:

    - Top-level CLOSURE(foo, lits...) which automatically generates
      foo_closure (along with foo_info, which we were doing already)

    - Array ANONYMOUS_CLOSURE(foo, lits...) which doesn't generate
      a foo_closure identifier.

Part of remove HEAP_ALLOCED patch set (#8199)

Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

Test Plan: validate

Reviewers: simonmar, austin

Subscribers: simonmar, ezyang, carter, thomie

Differential Revision: https://phabricator.haskell.org/D264

GHC Trac Issues: #8199