Fix setup_mark_lock missing prototype
(and do not call it if no parallel marker)

* include/private/pthread_support.h (GC_setup_mark_lock): Remove
prototype.
* misc.c (GC_init): Remove GC_setup_mark_lock call (move it to
GC_thr_init).
* pthread_support.c (setup_mark_lock): Rename from GC_setup_mark_lock;
add prototype (only if PARALLEL_MARK).
* pthread_support.c (GC_thr_init): Call setup_mark_lock() unless
available_markers_m1 is 0.
Relax mark_mutex attribute needed to disable elision (Linux/x64)

* pthread_support.c (setup_mark_lock): Pass PTHREAD_MUTEX_NORMAL
(instead of PTHREAD_MUTEX_ERRORCHECK) to pthread_mutexattr_settype
(actually, any valid settype call disables lock elision in glibc 2.19).
Update AUTHORS file
Also enable the TSX workaround for i386 (Linux)

* include/private/gcconfig.h (GLIBC_2_19_TSX_BUG): Define for
LINUX/I386 (if __GLIBC__).
Fix darwin_stop_world.c broken by 'thread_get_state fix' for other targets

* darwin_stop_world.c: Include Darwin-specific headers (sys/sysctl.h,
mach/machine.h) only if GC_DARWIN_THREADS.