create_builddir: add hw_imx53 (TrustZone) target

Until now, the HW platform support for the TrustZone features of the
i.MX53 boards could only be used, when adding a "trustzone" SPEC variable
manually. This commit adds a create_builddir target for HW i.MX53 with
TrustZone features enabled, fo convenience reasons.
run: wait some time before loading images via JTAG

When powering up the device it sometimes needs some seconds before the
bootloader prepared the board to use JTAG uploading.
python.run: make xmllint happy

This patch removes the XML-lookalike content from the inline config node
if the test-python program.
fixup "run: check XML syntax of generated config files"

Perform XML syntax check using a dedicated function, which can be
overwritten by the run script to explicitly suppress the syntax check.
Disable config syntax check for tool-chain test
resource_yield test: fix race condition
hw: set pages shareable in SMP systems only

Fixes #1181
os: extend on_alarm() by unsigned count value

The count value can be used to batch timeouts. I.e., if a periodic
timeout triggered multiple times before the timer had a chance to
process them, the count corresponds to the number of passed periods.
alarm: use on_alarm(count) feature
timer: apply PIT quirk to avoid high cpu load
vbox: mouse queue quirk
vbox: add LPT3 to ioport whitelist
vbox: use priorities in run scripts

By using priorities, we make sure that the timer gets scheduled whenever
it is able to run regardless of how much load is on the system.
vbox: disable some exits to get TinyCore running
fixup: "hw: set pages shareable in SMP systems only"