Add memory leak checking

Add checks that the vboot library does not leak memory. This works by
tracking VbExMalloc() calls and making sure that they have an associated
VbExFree().

Adjust host_signature to use VbExFree() instead of free(), so that this
scheme works correctly for existing code.

BUG=chrome-os-partner:21115
BRANCH=pit
TEST=FEATURES=test emerge-peach_pit vboot_reference

Change-Id: I6ccccfbcc162fc43fb75862cd0eddad78ce8b18a
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/66175
17 files changed