* configure.in: Handle --disable/enable-win32-registry.
        * install.texi: Document --disable/enable-win32-registry.
        * acconfig.h (ENABLE_WIN32_REGISTRY): New macro.
        (WIN32_REGISTRY_KEY): New macro.
        * prefix.c: Use to enable/disable win32-specific code.
        (lookup_key): Use versioned key.
        * configure: Regenerate.
        * config.in: Likewise.

From-SVN: r28712