Fix the handle locking in stdio

Fix the handle locking in stdio to use flockfile/funlockfile
internally when and where required.  Macros in <stdio.h> are updated
to automatically call the underlying functions when the process is
threaded to obtain the necessary locking.  A private mutex is added
to protect __sglue, the internal list of FILE handles, and another
to protect the one-time initialization.  Some routines in libc that
use getc() change to use getc_unlocked() as they're either protected
by their own lock or aren't thread-safe routines anyway.

Based on OpenBSD change by guenther@openbsd.org
http://www.mail-archive.com/source-changes@cvs.openbsd.org/msg01015.html

Bug: 3446659
Change-Id: Ie82116e358c541718d6709ec45ca6796be5a007b
diff --git a/libc/stdio/fclose.c b/libc/stdio/fclose.c
index e94292b..8c3bac4 100644
--- a/libc/stdio/fclose.c
+++ b/libc/stdio/fclose.c
@@ -36,9 +36,6 @@
 #include <stdlib.h>
 #include "local.h"
 
-/* BIONIC: remove any file lock associated with a FILE* pointer */
-extern void __fremovelock(FILE *fp);
-
 int
 fclose(FILE *fp)
 {
@@ -48,6 +45,7 @@
 		errno = EBADF;
 		return (EOF);
 	}
+	FLOCKFILE(fp);
 	WCIO_FREE(fp);
 	r = fp->_flags & __SWR ? __sflush(fp) : 0;
 	if (fp->_close != NULL && (*fp->_close)(fp->_cookie) < 0)
@@ -58,8 +56,8 @@
 		FREEUB(fp);
 	if (HASLB(fp))
 		FREELB(fp);
-	fp->_flags = 0;		/* Release this FILE for reuse. */
 	fp->_r = fp->_w = 0;	/* Mess up if reaccessed. */
-	__fremovelock(fp);
+	fp->_flags = 0;		/* Release this FILE for reuse. */
+	FUNLOCKFILE(fp);
 	return (r);
 }