Reduce sector 1 space pressure; further merge installer code

Reduce sector 1 space pressure; further merge installer code

Reduce sector 1 space pressure by moving objects that aren't needed by
Sector 1 proper into an "extended patch area".  While we're mucking
with the installer code, make the syslxint and extlinux installer code
even more similar.  It should now be pretty straightforward to
outright merge the code.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>