Added winpr functions to generate a stacktrace.
Added libcorkscrew headers for stacktrace on android.
Added execinfo.h detection for stacktrace on linux.
Winpr stacktrace header.
Fixed missing argument checks in logger, fixed crashes if file not created.
Fixed license header, added correct copyright.
Merge pull request #2038 from akallabeth/winpr-stacktrace

Winpr add stacktrace