Avoid unaligned reads on ARMv7

closes issue 137. Patch courtesy of throwaway-moar-arm++
conditionally set include dirs and install rules (e.g. --has-libuv)
Unbust the MSVC build.
Fix spell-o.
Add a way to specify a type needs finalization.

Nothing is done with this information as of yet, except storing it on
the type's STable.
update libuv from 0.11.18 to 0.11.29

This also includes minimal adjustments to our codebase, for example
callbacks only get a handle and not an additional status and uv_fs_read
wants an uv_but_t now instead of char*.
uv_fs_write also takes an uv_buf_t instead of char*
Workaround for Windows explosions in spawn.
Use indirect name for slot in p6opaque getattrs_n

This caused issues on PPC because the value of the register
is encoded in 16 bits while a string index is 32 bits wide.
This should have caused more issues, I might add. nwc10++
for finding the bug.
forcing a realclean to get rid of old libuv
Revert "Workaround for Windows explosions in spawn."

This workaraound is not needed when we remove old libuv files.
Base full collections of promotion rate.

There's no point doing a full GC every N collects if we're promoting
very little data each time. This patch, largely from timotimo++, uses
tracking of the number of bytes promoted to gen2 to decide when to do
it. This version of the patch correctly copes with blocked threads by
moving where we clear and contribute the promoted bytes.
Remove an unused variable; timotimo++.
Add objects needing finalization to finalize list.

Not using it for anything yet; this just makes sure objects with types
that have opted in to finalization reliably end up on the finalize
list of their allocating thread.
Allow per-HLL finalize handler installation.
Add force_gc instruction
Hopefully fix a warning.

Reported by JimmyZ++.
Start detecting objects needing finalize.

We don't do anything with them yet once we've detected they need to be
finalized, but this seems to get the detection of that case working.
Collect to-finalize objects into finalizing list.

This will later be used in order to pass them off to the finalize
handler in high level code.
Set up call to finalize handler if needed.

This means the rest can be wired up in HLL code.