Summary:
GHC's RTS contains ancient Zdecode code which changed format a bit.
It's easier to drop broken part and show original names.

The patch changes output for './hello +RTS -Da' (apply)
from such gibberish:

    stg_ap_v_ret... PAP/1(0x92922a, &i!_-&i!_:<.s_r=Z)
    stg_ap_0_ret... base:GHC.MVar.MVar(0x7fd3d1f040f8)
    stg_ap_v_ret... THUNK(&i!_-&i!_i!f.Z)
    stg_ap_v_ret... PAP/1(0x92c1f3, EO_:<.s_r=Z, EP_:<.s_r=Z)
    stg_ap_0_ret... ghc-prim:GHC.Tuple.(,)(0x7fd3d1f04209, 0x7fd3d1f041fa)
    stg_ap_0_ret... ghc-prim:GHC.Types.:(0x7fd3d1f04301, 0x7fd3d1f042ea)
    stg_ap_0_ret... THUNK(3F0_i!f.Z, 0x9152a1)
    stg_ap_0_ret... FUN/3(&s=_GHCziIOziFD_z/fB_ff=r=/IOFD14_i!f.Z)
    stg_ap_ppv_ret... FUN/3(&s=_GHCziIOziFD_z/fB_ff=r=/IOFD14_i!f.Z)
    stg_ap_0_ret... FUN/2(&s=_GHCziIOziFD_z/fIOD=vi:=FD15_i!f.Z)
    stg_ap_pv_ret... FUN/2(&s=_GHCziIOziFD_z/fIOD=vi:=FD15_i!f.Z)
    stg_ap_0_ret... base:GHC.IO.Handle.Types.FileHandle(5'A_:<.s_r=Z, 0x7fd3d1f04ef0)
    stg_ap_v_ret... THUNK(*>_&+_2__+/_i!f.Z, 0x7fd3d1f0602a, 0x7fd3d1f04f10)
    stg_ap_v_ret... PAP/1(0x7fd3d1f0602a, 0x7fd3d1f04f10)

to something more readable:

    stg_ap_v_ret... PAP/1(0x92922a, <Main_main_closure>[0x90b710])
    stg_ap_0_ret... base:GHC.MVar.MVar(0x7f1e256040f8)
    stg_ap_v_ret... THUNK(<Main_main_info>[0x4046c8])
    stg_ap_v_ret... PAP/1(0x92c1f3, <sEO_closure>[0x90b6f0], <sEP_closure>[0x90b6d0])
    stg_ap_0_ret... ghc-prim:GHC.Tuple.(,)(0x7f1e25604209, 0x7f1e256041fa)
    stg_ap_0_ret... ghc-prim:GHC.Types.:(0x7f1e25604301, 0x7f1e256042ea)
    stg_ap_0_ret... THUNK(<s3F0_info>[0x434f70], 0x9152a1)
    stg_ap_0_ret... FUN/3(<base_GHCziIOziFD_zdfBufferedIOFD14_info>[0x5f5198])
    stg_ap_ppv_ret... FUN/3(<base_GHCziIOziFD_zdfBufferedIOFD14_info>[0x5f5198])
    stg_ap_0_ret... FUN/2(<base_GHCziIOziFD_zdfIODeviceFD15_info>[0x5f7c60])
    stg_ap_pv_ret... FUN/2(<base_GHCziIOziFD_zdfIODeviceFD15_info>[0x5f7c60])
    stg_ap_0_ret... base:GHC.IO.Handle.Types.FileHandle(<r5qA_closure>[0x91a920], 0x7f1e25604ef0)
    stg_ap_v_ret... THUNK(<stg_ap_2_upd_info>[0x6b1c60], 0x7f1e2560602a, 0x7f1e25604f10)
    stg_ap_v_ret... PAP/1(0x7f1e2560602a, 0x7f1e25604f10)

First observed on '+RTS -Di' (interpreter) on unregisterised builds.

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>

Test Plan: built 'hello world' with -debug in moth modes and ran under '+RTS -Da'

Reviewers: simonmar, austin, ezyang

Reviewed By: austin, ezyang

Subscribers: phaskell, rwbarton, simonmar, relrod, ezyang, carter

Differential Revision: https://phabricator.haskell.org/D116