Use non-strict-ansi mode to build sources

Switch back to gnu++0x until the source can be compiled in strict ansi mode
with MinGW and Travis CI supports C++11 for GCC/Clang. This is -std is
supported by both clang and gcc.
Use Unix-compatible SDL include for SDL_thread
Use newer boost for C++-11 compatibility
Enable Travis CI build with clang
Fix swprintf call for _GLIBCXX_HAVE_BROKEN_VSWPRINTF

339ca50a57364b2509a6b5e7a073698038096a4d mixed code for GCC for Windows with
clang specific code. Just split this call in a clang again and a
_GLIBCXX_HAVE_BROKEN_VSWPRINTF specific implementation.
Use more widely used preprocessor defines for MinGW

6a46ad138c02138bb8f9a425afdec149bfa39182 switched from gnu style to strict
C++-11 style. The code still uses a lot of WIN32 preprocessor variable which
aren't defined in strict C++-11 mode. But the preprocessor variable _WIN32
seems to be defined just fine and is used now everywhere in the code.
Add extra includes and preprocessor checks for _WIN32