[m-rev.] diff: remove documenation for --enable-dotnet-grades option from configure

[Julien Fischer]

Remove documentation for --enable-dotnet-grades from configure.

The presence of the option --enable-dotnet-grades in the configure options
is confusing users.  Hide the documentation for it.

Delete the configure option --enable-minimal-hlc-trail-install which was
only ever added as a shortcut for members of the G12 project.  It's just
cluttering things up now.

configure.ac:
.INSTALL.in:
 	As above.

Julien.

diff --git a/.INSTALL.in b/.INSTALL.in
index db62cf1..150d756 100755
--- a/.INSTALL.in
+++ b/.INSTALL.in
@@ -155,10 +155,6 @@ make install
  #          The option --enable-stseg-grades causes the installation of grades
  #          that use stack segments.
  #
-#          The option --enable-dotnet-grades causes the installation
-#          of the .NET grades (see README.DotNet).  This grades are only
-#          installed if the .NET SDK is found.
-#
  #          The option --disable-java-grade prevents the installation of the
  #          Java grade.  The Java grade will be installed by default if the
  #          Java SDK is found.
diff --git a/configure.ac b/configure.ac
index a478283..7498d02 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3558,17 +3558,13 @@ AC_ARG_ENABLE(minimal-install,
          [install the minimal system required to bootstrap Mercury]),
      [enable_min_install="$enableval"],[enable_min_install="no"])

-AC_ARG_ENABLE(minimal-hlc-trail-install,
-    AC_HELP_STRING([--enable-minimal-hlc-trail-install],
-        [install the minimal system that supports trailing in a high level C grade]),
-    [enable_min_hlc_trail="$enableval"],[enable_min_hlc_trail="no"])
-
  # We don't enable the .NET grades by default because that may lead to
  # installation process breaking on Linux systems that have DotGNU or Mono
  # installed.
-#
+# NOTE: we deliberately do not document this option since it's only useful
+# for developers working on the .NET backend.
  AC_ARG_ENABLE(dotnet-grades,
-    AC_HELP_STRING([--enable-dotnet-grades], [install the .NET grades]),
+    AC_HELP_STRING([]),
      enable_dotnet_grades="$enableval",enable_dotnet_grades=no)

  AC_ARG_ENABLE(csharp-grade,
@@ -3873,13 +3869,6 @@ if test "$enable_ssdebug_grades" = yes; then
      esac
  fi

-# If this option is enabled then install a minimal system that supports
-# trailing in a high-level C grade.
-if test "$enable_min_hlc_trail" = yes
-then
-    LIBGRADES="$DEFAULT_BASE_GRADE.gc hlc.gc.trseg"
-fi
-
  # If this option is enabled then install only the grade that is being
  # used to build the compiler.
  # Also, override the grade that was chosen as the default grade above