Improve synchronization

- Fix bugs in kDos2Errno definition
- malloc() should now be thread safe
- Fix bug in rollup.com header generator
- Fix open(O_APPEND) on the New Technology
- Fix select() on the New Technology and test it
- Work towards refactoring i/o for thread safety
- Socket reads and writes on NT now poll for signals
- Work towards i/o completion ports on the New Technology
- Make read() and write() intermittently check for signals
- Blinkenlights keyboard i/o so much better on NT w/ poll()
- You can now poll() files and sockets at the same time on NT
- Fix bug in appendr() that manifests with dlmalloc footers off

third_party/dlmalloc/README.cosmo

@@ -1,21 +1,13 @@
-ORIGIN
+DESCRIPTION
 
-  http://gee.cs.oswego.edu/
+  malloc-2.8.6
+  written by Doug Lea
+
+LICENSE
+
+  http://creativecommons.org/publicdomain/zero/1.0/
 
 LOCAL CHANGES
 
-  Numerous local changes were made while vendoring Doug Lee's original
-  dlmalloc sources. Those changes basically boil down to:
-
-    1. Fewer #ifdefs
-    2. More modules (so linker can do a better job)
-    3. Delete code we don't need (cf. Knight Capital)
-    4. Readability / stylistic consistency
-
-  Since we haven't made any genuine improvements to Doug Lee's legendary
-  allocator, we feel this folder faithfully presents his intended work, in
-  harmony with Cosmopolitan conventions.
-
-  The only deleted code we're sure has compelling merit is the mspace
-  functionality. If we ever need memory pools, they might be more
-  appropriately vendored under //third_party/dlmalloc_mspace.
+  - Introduce __oom_hook()
+  - Favor pause (rather than sched_yield) for spin locks