Typical UNREG build failure looks like that:

  ghc-unreg/includes/Stg.h:226:46: error:
     note: in definition of macro 'EI_'
     #define EI_(X)          extern StgWordArray (X) GNU_ATTRIBUTE(aligned (8))
                                                  ^
      |
  226 | #define EI_(X)          extern StgWordArray (X) GNU_ATTRIBUTE(aligned (8))
      |                                              ^

  /tmp/ghc10489_0/ghc_3.hc:1754:6: error:
     note: previous definition of 'ghczmprim_GHCziTypes_zdtcTyCon2_bytes' was here
     char ghczmprim_GHCziTypes_zdtcTyCon2_bytes[] = "TyCon";
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
       |
  1754 | char ghczmprim_GHCziTypes_zdtcTyCon2_bytes[] = "TyCon";
       |      ^

As we see here "_bytes" string literals are defined as 'char []'
array, not 'StgWord []'.

The change special-cases "_bytes" string literals to have
correct declaration type.

Signed-off-by: Sergei Trofimovich <siarheit@google.com>