ProjectVersionMunged broken

ProjectVersionMunged is a configure variable defined like this (in aclocal.m4):

    # The version of the GHC package changes every day, since the     <-- should be "every time we configure"
    # patchlevel is the current date.  We don't want to force
    # recompilation of the entire compiler when this happens, so for
    # GHC HEAD we omit the patchlevel from the package version number.
    #
    # The ProjectPatchLevel1 > 20000000 iff GHC HEAD. If it's for a stable
    # release like 7.10.1 or for a release candidate such as 7.10.1.20141224
    # then we don't omit the patchlevel components.

    ProjectVersionMunged="$ProjectVersion"
    if test "$ProjectPatchLevel1" -gt 20000000; then
      ProjectVersionMunged="${VERSION_MAJOR}.${VERSION_MINOR}"
    fi
    AC_SUBST([ProjectVersionMunged])

However, since this bump from 8.5 to 8.6.0, ProjectVersionPatchLevel1 has always been set to 0, hence ProjectVersionMunged == ProjectVersion.

We have two options:

1. remove ProjectVersionMunged as no one noticed for two years and half
2. don't set ProjectVersionPatchLevel1 to 0 in HEAD