Use non-strict-ansi mode to build sources

The sources don't allow to be build in strict ansi mode. Thus the change from
GNU++11 mode to C++11 in 6a46ad138c02138bb8f9a425afdec149bfa39182 made building
the sources impossible. This was also catched by Travis CI but ignored by the
author and merged anyway.

Revert this change until the source can be compiled in strict ansi mode and
Travis CI support C++11.
Include correct SDL header in txfilter.cpp
use correct SDL include for SDL_thread
Fix preprocessor defines in build with GCC for windows

6a46ad138c02138bb8f9a425afdec149bfa39182 broke the build with GCC for windows
because it switched from gnu++0x to c++11. This not only makes the build fail
with more GCC version but also undefines the preprocessor variable WIN32. Thus
all windows specific code now fails to be handled correctly by the
preprocessor. But the preprocessor variable _WIN32 seems to be defined just
fine and is used now everywhere in the code.
Add missing includes and preprocessor checks
Fix swprintf call for _GLIBCXX_HAVE_BROKEN_VSWPRINTF

339ca50a57364b2509a6b5e7a073698038096a4d broke build with GCC for Windows for
code which was specific to windows. This should have never been mixed with
clang specific hacks.

Just split this call in a clang and a _GLIBCXX_HAVE_BROKEN_VSWPRINTF specific
implementation.