windows-mutex: New module. * lib/windows-mutex.h: New file, extracted from lib/glthread/lock.h. * lib/windows-mutex.c: New file, extracted from lib/glthread/lock.c. * lib/windows-spinlock.h: New file, extracted from lib/glthread/lock.h. * lib/glthread/lock.h: Include windows-spinlock.h, windows-mutex.h. (gl_spinlock_t): Remove type. (gl_lock_t): Define using glwthread_mutex_t. (gl_lock_initializer): Define using GLWTHREAD_MUTEX_INIT. (glthread_lock_init): Define using glwthread_mutex_init. (glthread_lock_lock): Define using glwthread_mutex_lock. (glthread_lock_unlock): Define using glwthread_mutex_unlock. (glthread_lock_destroy): Define using glwthread_mutex_destroy. (glthread_lock_init_func, glthread_lock_lock_func, glthread_lock_unlock_func, glthread_lock_destroy_func): Remove declarations. Use glwthread_spinlock_t instead of gl_spinlock_t. (gl_rwlock_initializer, gl_recursive_lock_initializer): Define using GLWTHREAD_SPINLOCK_INIT. * lib/glthread/lock.c (glthread_lock_init_func, glthread_lock_lock_func, glthread_lock_unlock_func, glthread_lock_destroy_func): Remove functions. * lib/glthread/cond.h: Use glwthread_spinlock_t instead of gl_spinlock_t. * modules/windows-mutex: New file. * modules/lock (Depends-on): Add windows-mutex.