Support read/write on socket file descriptors.

Add test_websockets_bi_fileops to test using read and write instead
of recv and send respectively. Uses same source files with
USE_FILE_OPS define.
Shared file-descriptor nums for files and sockets.

Also, add FS.createFileHandle(stream) and FS.removeFileHandle
functions for adding to and removing from the streams/file-descriptor
table.
Node issue 1669 was fixed and these tests work.
test_mmap works with Node now.
Remove unused llvm-extract stuff.
-nostdinc++ is needed to not pick up system C++ headers.

The comment here isn't quite accurate as at least current clang
requires that -nostdinc++ be passed for the correct behavior.

This was reported by Marcos Scriven.
There's no configuration global now.
Updated comment for DEAD_FUNCTIONS.
Update to r178253 from March 29, 2013.
Update libcxx to work with emscripten.
Update symbols.
Bump version.
Merge pull request #1008 from michaeljbishop/update-dead-functions-comment

Updated comment for DEAD_FUNCTIONS.
rephrase comment
Merge pull request #997 from waywardmonkeys/remove-extract

Remove unused llvm-extract stuff.
Merge pull request #1004 from waywardmonkeys/fix-nostdincxx

-nostdinc++ is needed to not pick up system C++ headers.
fix -nostdinc++
Merge pull request #1014 from waywardmonkeys/reinstate-tests

Reinstate tests
Merge pull request #1005 from waywardmonkeys/fix-cache-debugging

There's no configuration global now.
do not concatenate funcs_js parts, keep them separate