Introduce support for unlimited trampolines.

Introduce support for unlimited trampolines.

With this new code there is no longer an AOT compiler limit on the number of
trampolines, as they are allocated at runtime as necessary on iOS systems.
We use iOS's ability to remap a page to a different address in memory
and we replicate the trampolines we generate in the binary file to a
location in memory near a writable page where the trampolines can find the
specific runtime data needed (basically building writable constant pools).
On a big app like bcltests, this saves more than 900KB of binary size.
There is still the option to use the old code, by passing the "nopagetrampolines"
option tp the AOT compiler (the new code is the default).