winpr is now always build as single library.
The build option MONOLITHIC_BUILD doesn't influence this behavior anymore.
The only exception is winpr-makecert-tool which is still build as extra
library.
This obsoletes complex_libraries for winpr.
* set last error to ERROR_ENVVAR_NOT_FOUND in GetEnvironmentVariableA
if not found
* remove unused variables in SetEnvironmentVariableA
* add more test cases