Enable tail calls on ARM by default, with some
basic tests.

This has been well tested on Darwin but not elsewhere.
It should work provided the linker correctly resolves
  B.W  <label in other function>
which it has not seen before, at least from llvm-based
compilers.  I'm leaving the arm-tail-calls switch in
until I see if there's any problems because of that;
it might need to be disabled for some environments.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106299 91177308-0d34-0410-b5e6-96231b3b80d8
7 files changed