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\"");