don't enable backtrace() for stacktrace capturing by default

Because we don't yet have a treatment for deadlocks that are caused by
(recursive) use of malloc from within that facility.
issue-610: introduced TCMallocGetenvSafe

This is version of GetenvBeforeMain that's available to C code.
issue-610: made dynamic_annotations.c use TCMallocGetenvSafe
issue-610: use TCMallocGetenvSafe from inside malloc

Instead of plain getenv. So that windows getenv implementation that
may call malloc does not deadlock.
updated NEWS for 2.2rc
bumped version to 2.1.90
issue-620: windows dll patching: fixed delete of old stub code

After code for issue 359 was applied PreamblePatcher started using
it's own code to manage memory of stub code fragments. It's not using
new[] anymore. And it automatically frees stub code memory on
Unpatch.

Clearly, author of that code forgot to remote that no more needed
delete call. With that delete call we end up trying to free memory
that was never allocated with any of known allocators and crash.
updated NEWS for 2.2
bumped version to 2.2
issue-626: Fix SetupAggressiveDecommit initialization

This patch fixes the SetupAggressiveDecommit initialization to run after
pageheap_ creation.  Current code it not enforcing it, since
InitStaticVars is being called outside the static_vars module.
eliminated CheckIfKernelSupportsTLS

We don't care about pre-2.6.0 kernels anymore. So we can assume that
if compile time check worked, then at runtime it'll work.
avoid recursion in backtrace()
extended low_level_alloc

By adding ability to customize pages allocator
implemented emergency malloc
mark