changes of flags and fp lock.
* libc/stdio/freopen.c: Ditto.
* libc/stdio/freopen64.c: Ditto.
* libc/stdio/fgetc.c: Revert change from 2009-04-24, remove sfp locks
which guard entire function to avoid potential deadlocks when using
stdio functions in multiple thraeds.
* libc/stdio/fgets.c: Ditto.
* libc/stdio/fgetwc.c: Ditto.
* libc/stdio/fgetws.c: Ditto.
* libc/stdio/fread.c: Ditto.
* libc/stdio/fseek.c: Ditto.
* libc/stdio/getc.c: Ditto.
* libc/stdio/getdelim.c: Ditto.
* libc/stdio/gets.c: Ditto.
* libc/stdio/vfscanf.c: Ditto.
* libc/stdio/vfwscanf.c: Ditto.
* libc/stdio/fflush.c (_fflush_r): Split out core functionality into
new function __sflush_r. Just lock file and call __sflush_r from here.
* libc/stdio/fwalk.c (_fwalk): Remove static helper function and move
functionality back into main function. Don't walk a file with flags
value of 1. Add comment.
(_fwalk_reent): Ditto.
* libc/stdio/local.h (__sflush_r): Declare.
* libc/stdio/refill.c (__srefill): Before calling fwalk, set flags
value to 1 so this file pointer isn't walked. Revert flags afterwards
and call __sflush_r for this fp if necessary. Add comments.
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