libc: Fix sem_post() implementation to wake up all waiting threads.

This also allows us to optimize the case where we increment an
uncontended semaphore (no need to call futex_wake() then).

Change-Id: Iad48efe8551dc66dc89d3e3f18c001e5a6c1939f
diff --git a/libc/unistd/sysconf.c b/libc/unistd/sysconf.c
index 27b113c..9377802 100644
--- a/libc/unistd/sysconf.c
+++ b/libc/unistd/sysconf.c
@@ -44,7 +44,7 @@
 #define  SYSTEM_MQ_OPEN_MAX     8
 #define  SYSTEM_MQ_PRIO_MAX     32768
 #define  SYSTEM_SEM_NSEMS_MAX   256
-#define  SYSTEM_SEM_VALUE_MAX   (2147483647)
+#define  SYSTEM_SEM_VALUE_MAX   0x3fffffff  /* see bionic/semaphore.c */
 #define  SYSTEM_SIGQUEUE_MAX    32
 #define  SYSTEM_TIMER_MAX       32
 #define  SYSTEM_LOGIN_NAME_MAX  256