Streaming I/O and support of named pipes (#570)

* added streaming i/o for scripting, and a byteutil.get_size function

* added i/o stream class, also added named pipes support on lua side via ffi

* added constant file.named_pipes_prefix

* added buffered and yield modes for io_stream

* added new time function for work with UTC - utc_time, utc_offset, local_time

* docs updated

* constant pid moved to os.pid

* now gmtime_s and localtime_s used only in windows

res/modules/internal/stream_providers/named_pipe.lua

@@ -0,0 +1,7 @@
+local FFI = ffi
+
+if FFI.os == "Windows" then
+    return require "core:internal/stream_providers/named_pipe_windows"
+else
+    return require "core:internal/stream_providers/named_pipe_unix"
+end