vfs and newlib: small fixes

- spaces->tabs in tasks.c
- update vfs_uart.c to use per-UART locks
- add license to vfs_uart.c
- allocate separate streams for stdout, stdin, stderr, so that they can be independently reassigned
- fix build system test failure

components/newlib/platform_include/esp_newlib.h

@@ -0,0 +1,27 @@
+// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef __ESP_NEWLIB_H__
+#define __ESP_NEWLIB_H__
+
+/**
+ * Function which sets up syscall table used by newlib functions in ROM.
+ *
+ * Called from the startup code, not intended to be called from application
+ * code.
+ */
+void esp_setup_syscalls();
+
+
+#endif //__ESP_NEWLIB_H__