* null-threads.h, pthread-threads.h

* null-threads.h, pthread-threads.h
(SCM_I_PTHREAD_RECURSIVE_MUTEX_INITIALIZER): Removed.
(scm_i_pthread_mutexattr_recursive): New.

* threads.c (scm_i_pthread_mutexattr_recursive): Declare.
(scm_i_critical_section_mutex): Do not initialize statically.
(scm_threads_prehistory): Initialize
scm_i_pthread_mutexattr_recursive and scm_i_critical_section_mutex
here.

* eval.c (source_mutex): Do not initialiaze statically.
(scm_init_eval): Do it here, using
scm_i_pthread_mutexattr_recursive.