[Truffle] Tags for new specs.

spec/truffle/tags/core/file/open_tags.txt

@@ -1,3 +1,6 @@
 fails:File.open opens a file with a file descriptor d and a block
 fails:File.open with a block propagates StandardErrors produced by close
 slow:File.open on a FIFO opens it as a normal file
+fails:File.open creates an unnamed temporary file with File::TMPFILE
+fails:File.open accepts extra flags as a keyword argument and combine with a string mode
+fails:File.open accepts extra flags as a keyword argument and combine with an integer mode

spec/truffle/tags/library/socket/basicsocket/recv_tags.txt

@@ -1,3 +1,4 @@
 fails:BasicSocket#recv receives a specified number of bytes of a message from another socket
 fails:BasicSocket#recv accepts flags to specify unusual receiving behaviour
 fails:BasicSocket#recv gets lines delimited with a custom separator
+fails:BasicSocket#recv allows an output buffer as third argument

spec/truffle/tags/library/socket/socket/accept_nonblock_tags.txt

@@ -1 +1,2 @@
 fails:Socket#accept_nonblock raises IO::WaitReadable if the connection is not accepted yet
+fails:Socket#accept_nonblock returns :wait_readable in exceptionless mode

spec/truffle/tags/library/socket/tcpsocket/recv_nonblock_tags.txt

@@ -1 +1,2 @@
 fails:TCPSocket#recv_nonblock returns a String read from the socket
+fails:TCPSocket#recv_nonblock returns :wait_readable in exceptionless mode

spec/truffle/tags/library/socket/unixserver/accept_nonblock_tags.txt

@@ -1,2 +1,3 @@
 fails:UNIXServer#accept_nonblock accepts a connection in a non-blocking way
 fails:UNIXServer#accept_nonblock returns a UNIXSocket
+fails:UNIXServer#accept_nonblock returns :wait_readable in exceptionless mode

spec/truffle/tags/library/stringio/external_encoding_tags.txt

@@ -0,0 +1 @@
+fails:StringIO#external_encoding does not set the encoding of its buffer string if the string is frozen