add static asserts for constants of untested architectures

- also remove version (X86 || X86_64) idiom
unittests with shared library

- add SHARED flag to posix.mak

- default to SHARED=1 on linux

- setting SHARED to a non-empty string implies PIC and
  builds a shared library for testing

- setting SHARED to an empty string builds a single
  executable for testing

- Add a moduleUnitTester that only runs a single unit test
  selected via a cmdline argument. This allows to run tests
  in parallel with a single executable/shared library.
restrict SHARED to linux_64
Merge pull request #447 from dawgfoto/SharedRuntime_7

unittests with shared library
improve callWithStackShell

- compatible with LDC's inline asm
- only push callee save registers
fix random crash with -cov
Merge pull request #426 from dawgfoto/callWithStackShell

improve callWithStackShell
Merge pull request #449 from WalterBright/fixcovercrash

fix random crash with -cov
fix Issue 9726 - Add minimum % coverage required for -cov testing
Mark the floating-point environment as __gshared

It is not a thread-local variable.
Merge pull request #450 from WalterBright/fix9726

fix Issue 9726 - Add minimum % coverage required for -cov testing
Remove unused Object.opEquals(Object, Object)

It was added at 1e7ddf0425050e4f184532ec1d99316c37a8b2eb, but it seems to me that had not been used entirely.
Merge pull request #454 from donc/fenv_gshared

Mark the floating-point environment as __gshared
remove unused tls.S
integrate remaining rt.memory_osx into rt.sections_osx
make Thread.sm_this a plain TLS value

- this became possible, because the TLS emulation
  no longer uses the Thread.getThis() instance

- Windows use impersonate_thread to set sm_this
  when attaching a foreign thread
Merge pull request #456 from dawgfoto/useTLS

make Thread.sm_this a plain TLS value
Revert "Merge pull request #456 from dawgfoto/useTLS"

This reverts commit dee2d7576ca94a21706f64d83ff9b0dfe761a7b1, reversing
changes made to bf0eefe3b2dda5fde25e8070f635e4a8e2deb042.
Merge pull request #457 from AndrejMitrovic/Revert456

Revert "Merge pull request #456 from dawgfoto/useTLS"
lazily initalize TLS block on first access