Arrangements for the SIGSEGV perf tester.

Sync with the new SIGSEGV API.

Fix NQD bounds checking -- don't overwrite the CLEAR Page Guard.

Use NQD dirty boxes, VOSF backend
+ make video_vosf_profitable() NQD accel aware
+ call vm_protect() only if PFLAG_CLEAR(page)

Remove obsolete Cygwin/X11 addressing hack. Fix DirectX fullscreen mode
with hardware surface. On the other hand, DIB (SDL_VIDEODRIVER=windib)
always seems the fastest on my system for both windowed and fullscreen
modes.

Improve SDL/fullscreen mode when not used in DGA mode, i.e. cases when
screen needs to be updated too. This needs better boxes characterisation.

Fix DGA when visible screen is smaller than virtual display, aka fix
fullscreen mode when VidMode extension is enabled. Also fix SDL fullscreen
to really update the screen as this is necessary by default on Linux since
simple windowed is used (and not DGA for fullscreen).

Always prefer the 64 pixel chunks update code.

Rearrange B2 video_x.cpp to match video_vosf.h updates

Enable multiple depths in fullscreen DGA modes, i.e. add 1-bit to 16/32-bit
blitters, rewrite update_display_dga_vosf() to actually work with sub byte
pixels. Factor out update_display_window_vosf() since it's long time that
it is no longer checking for first column and last column that have changed.

s/vm_page_size/vm_get_page_size/ to avoid name clash on MacOS X

lock X11 display better around update_display_window_vosf()

Don't try to make a cast value an lvalue (Brian Johnson). Add some explicit
casts to (int) in order to avaoid this warning:
warning: comparison between `const enum video_depth' and `enum <anonymous>'

Try a better VOSF run-time performance check heuristic.

Move VideoMode wrappers to video_blit.h.

Happy New Year! :)

use spinlocks on SheepShaver/Linux/PPC, and possibly others where spinlocks
are available. TODO: check the fastest & safest means to lock VOSF stuff.

Rearrange video_vosf.h to accomodate both SheepShaver and BasiliskII video
infrastructure. Make video_blit.cpp a little more emulator independent.

- added infrastructure for multi-monitor support; only video_x.cpp is
  converted for the new scheme; not actually tested with a mult-monitor
  setup yet but at least single-monitor display doesn't seem to be broken
  (UAE banked addressing would definitely require some extensions to handle
  multiple frame buffers)
- struct video_mode has an extra field that is free for use by platform-
  specific code

- video_x.cpp: the_buffer shall always be mapped through vm_alloc() so
  that it can be vm_protect()'ed at will afterwards
- video_x.cpp: let driver_base free() the_buffer_copy and the_host_buffer,
  if necessary
- video_vosf.h: reverted to use malloc() for mainBuffer.dirtyPages and
  mainBuffer.pageInfo
- vm_alloc.cpp: small cleanups
- fixed typos

- added video_vosf_init()/video_vosf_exit() for initialization and destruction
  of the internal structures used for the VOSF system
- use vm_acquire()/vm_release() for VOSF buffers and hope the_buffer is
  allocated above RAM address space (temporary workaround for 64-bit
  addressing systems)
- don't free() screen buffers in driver_base dtor
- don't free() memory mapped buffers in driver_base dtor

- added support for platform-independant mutexes, currently only properly
  implemented under Unix
- adb.cpp uses mutexes for thread-safe mouse handling
- video_x.cpp: pressing Ctrl-F5 in windowed mode switches to a "grabbed"
  relative mouse mode, useful for some games
- video_x.cpp: fixed some bugs relating to the hotkeys (key releases are no
  longer treated as hotkeys)

added support for 8-bit windowed modes on 16 and 32-bit screens (for the
games, man, the games! :-)

- experimental gamma table support
- restructured video_x.cpp: uses classes for display types

video_x.cpp supports resolution switching in windowed mode: the available
resolutions are 512x384, 640x480, 800x600, 1024x768 and 1280x1024 (the prefs
editor has to be updated to reflect this). The resolution selected in the
prefs editor is used as the default, but it can be changed in the Monitors
control panel. So far only tested with direct addressing.

- added SIGSEGV support for Linux/Alpha (to be checked), Darwin/PPC
- added uniform virtual memory allocation
  (supports mmap(), vm_allocate(), or fallbacks to malloc()/free())
- cleaned up memory allocation in main_unix.cpp

added patches from Brian J. Johnson (better VOSF performance and responsiveness)

Mainly changes to the VOSF code:
- improved blitters selection
- improved blitters performance if UNALIGNED_PROFITABLE is set
- cleaned up 8 bpp blitters

Changes made to the update routines
- Cleaned up the process for determining the ranges of pages touched
  that have to be blitted onto the screen (find_next_page_set() and
  find_next_page_clear() functions)
Changes made to do_handle_screen_fault()
- An unhandled address is now dealt by the default SIGSEGV handler
- Print out the address of the instruction that caused the exception

fixed fbcopy_16_obo on big-endian systems

- replaced floating-point page shift calculation by integer routine, fixing
  the VOSF problems under NetBSD/m68k
- fixed off-by-7 error in 1-bit window update routines

added SA_SIGINFO to sa_flags when sa_sigaction is used

- fbcopy_raw now works if memcpy() is not used
  (but it seems better to use memcpy since GCC has inline equivalent)

- video on SEGV signals