mingw build on appveyor uses undefined vsnprintf

[James E. King, III]

While building Boost.Random which uses Boost.Test, the build fails on mingw on appveyor (not MinGW-w64 however, that seems to work).

PR: ​https://github.com/jeking3/random/pull/1

Failed Job: ​https://ci.appveyor.com/project/jeking3/random/build/1.0.17-develop/job/n3h2iw03mrebw8wq

Specific failure:

gcc.compile.c++ bin.v2\libs\test\build\gcc-mingw-gnu-5.3.0\release\threadapi-win32\execution_monitor.o
In file included from libs\test\src\execution_monitor.cpp:16:0:
./boost/test/impl/execution_monitor.ipp: In function 'void boost::detail::report_error(boost::execution_exception::error_code, const boost::exception*, const char*, char**)':
./boost/test/impl/execution_monitor.ipp:216:84: error: 'vsnprintf' was not declared in this scope
 #  define BOOST_TEST_VSNPRINTF( a1, a2, a3, a4 ) vsnprintf( (a1), (a2), (a3), (a4) )
                                                                                    ^
./boost/test/impl/execution_monitor.ipp:241:5: note: in expansion of macro 'BOOST_TEST_VSNPRINTF'
     BOOST_TEST_VSNPRINTF( buf, sizeof(buf)-1, format, *args );
     ^
    "g++"   -O3 -finline-functions -Wno-inline -Wall -pedantic -march=i686 -m32 -Wno-variadic-macros -std=c++03 -DBOOST_ALL_NO_LIB=1 -DBOOST_CHRONO_DYN_LINK=1 -DBOOST_CHRONO_THREAD_DISABLED -DBOOST_SYSTEM_DYN_LINK=1 -DBOOST_SYSTEM_NO_DEPRECATED -DBOOST_TEST_DYN_LINK=1 -DBOOST_TIMER_DYN_LINK=1 -DNDEBUG  -I"." -c -o "bin.v2\libs\test\build\gcc-mingw-gnu-5.3.0\release\threadapi-win32\execution_monitor.o" "libs\test\src\execution_monitor.cpp"
...failed gcc.compile.c++ bin.v2\libs\test\build\gcc-mingw-gnu-5.3.0\release\threadapi-win32\execution_monitor.o...

[Raffi Enficiaud]

Would this ​https://stackoverflow.com/a/43405963/1617295 work for you?

[Raffi Enficiaud]

Should be fixed through GH PR 145