* Selected correct PROTO define for __MSVC__.
* Renamed static function min to minimum to prevent conflict in MSVC.
* Added condition __MSVC__ when __attribute( ( unused ) ) was used.
* Added {} in classes.c to prevent local variable definitions which
are not allowed in MSVC for c files.
* Added xgetopt.cc/xgetopt.h for getopt functionality.
* Added SCL_EXPRESS_DLL_IMPORTS/SCL_EXPPP_DLL_IMPORTS to CMakeLists.txt.
* Added scl_export.h with conditional flags for import/export.
* Added SCL_EXPRESS_EXPORT flag for all global variables in headers.
* Added SCL_EXPRESS_EXPORT flag for all function prototypes in headers.
* Added SCL_EXPRESS_DLL_EXPORTS flag for express CMakeLists.txt