libc/locale: Use iconv from upstream musl

Use iconv.c from upstream musl to clean up the include path hack added in
commit 480ce64 ("libc: add include path for locale").

The diff between our version and the musl version looks like this:

[penberg@localhost osv]$ diff -u libc/locale/iconv.c musl/src/locale/iconv.c
--- libc/locale/iconv.c	2013-10-25 12:11:24.042750927 +0300
+++ musl/src/locale/iconv.c	2014-08-04 17:07:25.446850394 +0300
@@ -316,8 +316,8 @@
 			}
 			d = c;
 			for (c=0; c<128-totype; c++) {
-				if (d == legacy_chars[ map[c*5/4]>>2*c%8 |
-					map[c*5/4+1]<<8-2*c%8 & 1023 ]) {
+				if (d == legacy_chars[ tomap[c*5/4]>>2*c%8 |
+					tomap[c*5/4+1]<<8-2*c%8 & 1023 ]) {
 					c += 128;
 					goto revout;
 				}

but this is because the imported copy is from January 2013 or earlier:

  [penberg@localhost osv]$ git log libc/locale/iconv.c
  commit 79d5ad7d6f7bbcc20edf2ce2bbf3cc08f04b08dd
  Author: Christoph Hellwig <hch@lst.de>
  Date:   Thu Jan 17 09:33:18 2013 +0100

      import locale support and all dependencies from musl

but our musl version in the git submodule is from February 2013.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
net: drop custom net_channel allocators

Once upon a time, allocating a page was much faster than allocating half
a page, so we used a custom allocator.

These days, it's just as fast, and the custom allocator interferes with
memory debugging.

Signed-off-by: Avi Kivity <avi@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>