x-djgpp: Delete code that conditionally modifies target_alias.

x-djgpp: Delete code that conditionally modifies target_alias.

        * i386/x-djgpp: Delete code that conditionally modifies target_alias.
        Delete code that conditionally modifies 'version'.
        Delete X_CPPFLAGS. Add comment for SYSTEM_HEADER_DIR.
        * i386/xm-djgpp.h (GCC_DRIVER_HOST_INITIALIZATION): New macro.
        * gcc.c (main): Use it.
        * config/i386/xm-djgpp.h (UPDATE_PATH_HOST_CANONICALIZE): New macro.
        * prefix.c (update_path): Use it.
        * i386/djgpp.h (STANDARD_INCLUDE_DIR): Define.
        (MD_EXEC_PREFIX): Set to '/dev/env/DJDIR/bin/'.
        (ASM_OUTPUT_SECTION_NAME): Add code attribute to sections containing
        code.
        (SUPPORTS_WEAK, SUPPORTS_ONE_ONLY): Default to true.
        (SUBTARGET_SWITCHES): Adjust.
        (WCHAR_UNSIGNED, WCHAR_TYPE_SIZE, WCHAR_TYPE): Undefine before
        defining.
        (WINT_TYPE, SIZE_TYPE, PTRDIFF_TYPE): Define.

From-SVN: r35484