prevent HashTab manipulation during opApply iteration
Fix Issue 10897 - btc, btr and bts shouldn't be safe
low-level implementation of dynamic loading

- implement rt_loadLibrary/rt_unloadLibrary in src/rt/sections_linux.d
- keep hashmap from link_map* to DSO* structs to gather library
  dependencies and perform thread initialization
- thread local reference count to trigger TLS ctors/dtors
- add core.thread interface to inherit loaded libraries when spawning
  a new Thread
- make dynamic loading functions only available for version (Shared)
- set -version=Shared when building a shared druntime
- loading a shared library when statically linking against druntime
  will cause a link error
- Runtime.loadLibrary and Runtime.unloadLibrary are templated so that
  they are only linked when actually used
- the static libphobos2.a does not depends on libdl
add unittests for shared libraries

- test EH, GC, init/fini and ModuleInfos for linked and loaded D libraries
add C tests

- linkD - links a D library
- loadD - links druntime, loads a D library
- loadDR - loads druntime, loads a D library
add tests with dependent libraries
add test for C host with D plugins
Merge pull request #593 from dawgfoto/dynamicLoading

dynamic loading
Merge pull request #595 from dawgfoto/fixupHashTab

prevent HashTab manipulation during opApply iteration
fixed int-uint comparisons
fixed more int-uint comparisons
Fixed more signed/unsigned comparisons
Merge pull request #596 from monarchdodra/bt

Fix Issue 10897 - btc, btr and bts shouldn't be safe
Add types for Linux/AArch64.

Only implementation of core.thread is missing.
Merge pull request #602 from redstar/aarch64

Add types for Linux/AArch64.
Add missing types for Linux/ARM.

Only implementation of core.thread is missing.
Interface to the POSIX System logger interface.
http://pubs.opengroup.org/onlinepubs/007904875/basedefs/syslog.h.html
Merge pull request #603 from redstar/arm

Add missing types for Linux/ARM.
fix glibc links for bits/dlfcn.h
Added versions for Linux, OSX, FreeBSD and Solaris.