- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Make the RTC checking for QEMU even more aggressive.

At work, where we use use KVM+QEMU, we notice that pxeboot is pratically
impossible because of network timeouts. This is due to the fact that the
RTC code makes aggressive jumps.

Two RTC reads does not seem to be sufficient. Change the code to check
for 8 identical RTC values.

Sponsored by: Kumina bv

Implement a workaround for a long-standing problem in
libi386's time(), caused by a qemu bug. The bug might
be present in other BIOSes, too.

qemu either does not simulate the AT RTC correctly or
has a broken BIOS 1A/02 implementation, and will return
an incorrect value if the RTC is read while it is being
updated.

The effect is worsened by the fact that qemu's INT 15/86
function ("wait" a.k.a. usleep) is non-implmeneted or
broken and returns immediately, causing beastie.4th to
spin in a tight loop calling the "read RTC" function
millions of times, triggering the problem quickly.

Therefore, we keep reading the BIOS value until we get
the same result twice. This change fixes beastie.4th's
countdown under qemu.

Approved by: des (mentor)

Use __FBSDID().
Also some minor copyright style cleanups.

Cleanup warnings. Most of these are signed/unsigned warnings, as well as
some added const's.

Substantially revamp the way that we determine the amount of memory available
for our use. Use the same search order for BIOS memory size functions
as the kernel will later use.

Allow the loader to use all of the detected physical memory (this will
greatly help people trying to load enormous memory disk images).

More correctly handle running out of memory when loading an object.

Use the end of base memory for the top of the heap, rather than
blindly hoping that there is 384k left.

Add copyrights to a couple of files I forgot.

Fix comment to match code

Initial integration of the i386 bootloader and BTX.

- Discard large amounts of BIOS-related code in favour of the more compact
BTX vm86 interface.
- Build the loader module as ELF, although the resulting object is a.out,
make gensetdefs 32/64-bit sensitive and use a single copy of it.
- Throw away installboot, as it's no longer required.
- Use direct bcopy operations in the i386_copy module, as BTX
maps the first 16M of memory. Check operations against the
detected size of actual memory.