GXemul Code2

Some cleanup and clarifications.

Add missing <p>.

Moving commented out fsync from diskimage_scsicmd.cc to diskimage.cc. Treat partial reads (e.g. at end of a disk image) as OK.

Screenshot of NetBSD/playstation2 reaching userland.

Adding comment about NetBSD/evbmips Malta INSTALL ramdisk kernel.

Adding automated regression testing expect script for NetBSD 8.0/pmax.

Writing a more reasonable section about Loads and Stores; removing the "address translation" section.

Adding __builtin_expect (likely/unlikely) detection to the configure script.

Time to run test/test_netbsd_pmax_install.sh
--------------------------------------------

likely() put in the hot path of the MIPS load/store implementation
(actually unlikely()).

clang 6.0.0 without likely(): with likely():

without -flto: 244.13 seconds 242.81 seconds
with -flto: 230.?? seconds 229.42 seconds

g++ 8.3.0 without likely(): with likely():

without -flto: 232.40 seconds 232.78 seconds
with -flto: 231.88 seconds 228.56 seconds

Not very noticable, but I'll leave them in, for now.

Fix warning about undefined behavior, as printed by gcc when used with -flto.

Add an example of using setroot to play with booting, even though there is no keyboard support.