CONSTR_NOCAF was introduced with 55d535da as a replacement for
CONSTR_STATIC and CONSTR_NOCAF_STATIC, however, as explained in Note
[static constructors], we copy CONSTR_NOCAFs (which can also be seen in
evacuate) during GC, and they can become dead, like other CONSTR_X_Ys.
processHeapClosureForDead is updated to reflect this.

Test Plan: Validates on x86_64. Existing failures on i386.

Reviewers: simonmar, bgamari, erikd

Reviewed By: simonmar, bgamari

Subscribers: rwbarton, thomie, carter

GHC Trac Issues: #7836, #15063, #15087, #15165

Differential Revision: https://phabricator.haskell.org/D4928

(cherry picked from commit 2625f131)