STYLE: Fixed documentation of how to produce forwarding executables for multi-configuration builds with CMAKE_INTDIR.

BUG: When a "wrong argument" was detected, we call the WrongArgument handler. If the handler returns success, the argument parsing should continue. Currently, it was stopping parsing immediately after the wrong argument was processed, irrespective of the WrongArgument handler status. Fixed that.

BUG: FileIsDirectory would remove the trailing '/' even when the path is indeed the root i.e. '/'. Hence the test would be incorrect for root directory. Fixed that.

ENH: Adding stringstream compatibility implementation.  It is currently identical to ostringstream.  Fixed local variable pcount hiding method warning.

BUG: revert yesterday patch. The implementation was correct. The problem was that _WIN32 was forced to be #define on cygwin when included from ITK, which was miss matching the implementation from the declaration. Put extra condition for CYGWIN system

BUG: Make sure to use the Win32 interface (HINSTANCE) for handling shared lib on cygwin and mingw system