Also replace boost::detail::atomic_exchange_and_add for the interpreter.

Generalize the __cxa_atexit replacement to cover more symbols.
Because the JIT cannot handle inline asm, provide compiled symbols for relevant
functions until cling has switched to MCJIT.
This fixes the use of many boost libraries (e.g. regex) in cling on x86_64/i386.
Kudos to Marco Clemencic for the idea!
Fix non-GCC (and non-thread-safe!) case.
Fix func/ptr cast warning; work around MSVC2012 lack of C++11.
Work-around transaction unload not informing MetaSema.

When a file is unloaded its entry should be removed from MetaSema::m_WaterMarks.
At the moment the corresponding callback is not implemented.

Instead, we also record the relation <Transaction*,Entry*>, so that upon
MetaSema requesting an unload, we can clean-out the corresponding data
from m_WaterMarks.

In addition, to catch the case where the target transaction (unloadPoint)
is not longer present we issue an error and do not unload anything.
Protect from missing CodeGen.
Survive and signal non-unique lookup results.
Survive lookup in a forward declared context.
Fix some of the error messages when starting cling.exe on Windows

Fixes the following error messages:
The system cannot find the path specified.
ERROR in cling::CIFactory::createCI(): cannot extract standard library include paths!
Invoking:
    echo | LC_ALL=C C:/Program Files (x86)/Microsoft Visual Studio 11.0/VC/bin/cl.exe  /DWIN32 /D_WINDOWS /W3    -xc++ -E -v - 2>&1 >/dev/null | awk '/^#include
 </,/^End of search/{if (!/^#include </ && !/^End of search/){ print }}' | grep -E "(c|g)\+\+"
results in
The system cannot find the path specified.
with exit code 255
Warning in cling::CIFactory::createCI():
  C++ ABI check not implemented for this standard library

Note there are still a few remaining errors at startup time:

error: cannot mangle RTTI descriptors for type 'exception' yet
error: cannot mangle the name of type 'exception' into RTTI descriptors yet

Apparently coming from the following statement (at line 284 in Interpreter.cpp, in Interpreter::IncludeCXXRuntime()):

    declare("#include \"cling/Interpreter/ValuePrinter.h\"");
Check in the system registry for the version of Visual Studio with which we compiled cling (instead of the highest version)
CLING_CXXABI* is unused for MSVC.
Fix input files processing (cling foo.c should work now)
Adding test for ROOT-6244 (test_exec_in_same_dir.C)
Add protection against missing CodeGen.
Add versioning.
After the 'tag' switch to a dev version.
After the 'tag' switch to the 'right' dev version.