Allow compiling and using as DLL in windows#502

Merged

foonathan merged 3 commits intofmtlib:masterfrom AbberiorInstruments:fmt-api-printf-fix

May 5, 2017

+32-27

Commits on Apr 27, 2017

printf.h fixed to compile clean - need to check whether this is the right
AndreasSchoenle
committed
fix warnings and errors in test compiles with BUILD_SHARED_LIBS
AndreasSchoenle
committed

Commits on Apr 30, 2017

did requested changes and added one change to allow all tests to succeed
AndreasSchoenle
committed