mingw-w64 pthread.h header: missing 'const' specifier in pthread_attr_getschedpolicy()

[Lukas Kucera]

In the pthread.h header, the pthread_attr_getschedpolicy (pthread_attr_t *attr, int *pol) function is declared without 'const' specifier of pthread_attr_t argument. Correct definition should be: pthread_attr_getschedpolicy (const pthread_attr_t *attr, int *pol);