render the --enable-pch option inert.

configure.in

@@ -444,7 +444,7 @@ AC_ARG_ENABLE(vba,
 
 AC_ARG_ENABLE(pch,
     AS_HELP_STRING([--enable-pch],
-        [EXPERIMENTAL: Enables precompiled header support for C++.])
+        [DEPRECATED : is ignored])
 )
 
 AC_ARG_ENABLE(mozilla,
@@ -2642,23 +2642,7 @@ dnl ===================================================================
 dnl Set the ENABLE_PCH variable. (Activate --enable-pch)
 dnl ===================================================================
 AC_MSG_CHECKING([whether to enable pch feature])
-if test -n "$enable_pch" && test "$enable_pch" != "no"; then
-    if test "$_os" = "WINNT" -a "$WITH_MINGW" != "yes"; then
-        ENABLE_PCH="TRUE"
-        AC_MSG_RESULT([yes])
-dnl There is no PCH support in GCC versions prior to this
-    elif test "$GCC" = "yes"; then
-        ENABLE_PCH="TRUE"
-        AC_MSG_RESULT([yes])
-    else
-        ENABLE_PCH=""
-        AC_MSG_WARN([Precompiled header not yet supported for your platform/compiler])
-    fi
-else
-    ENABLE_PCH=""
-    AC_MSG_RESULT([no])
-fi
-AC_SUBST(ENABLE_PCH)
+AC_MSG_RESULT([no, obsolete])
 
 dnl ===================================================================
 dnl Search all the common names for GNU make

set_soenv.in

@@ -1812,7 +1812,6 @@ ToFile( "ENABLE_FONTCONFIG", "@ENABLE_FONTCONFIG@", "e" );
 ToFile( "FONTCONFIG_LIBS",   "@FONTCONFIG_LIBS@",   "e");
 ToFile( "FONTCONFIG_CFLAGS", "@FONTCONFIG_CFLAGS@", "e");
 ToFile( "ENABLE_DIRECTX",    "@ENABLE_DIRECTX@",    "e" );
-ToFile( "ENABLE_PCH",        "@ENABLE_PCH@",       "e" );
 ToFile( "ENABLE_GRAPHITE",   "@ENABLE_GRAPHITE@",   "e");
 ToFile( "SYSTEM_GRAPHITE",   "@SYSTEM_GRAPHITE@",   "e");
 ToFile( "GRAPHITE_LIBS",     "@GRAPHITE_LIBS@",     "e");