on MinGW32, use compiler provided [v]snprintf
release thread handle
Merge pull request #105 from pijyoi/master

win32 fixes
Updated for next release 1.3.3
Fixed #ifdef order in header file
Added printf formatting to send/sendm, deprecated sendf/sendfm
Added zsys class for non-portable file system functions
Cosmetic change
If zctx_interrupted is non-zero, does not install signal handler