Perform fine-tuning of socketpair and pipe

- removed unneeded share parameter from pipe on nt
- socktpair(type | SOCK_CLOEXEC) is now polyfilled
- use textwindows for linker micro-optimization
- apologies for auto clang-format diff noise :(
- improve socketpair docstring

See #122

libc/calls/createpipename.c

@@ -0,0 +1,47 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/alg/reverse.internal.h"
+#include "libc/calls/calls.h"
+#include "libc/nt/process.h"
+
+static const char kPipeNamePrefix[] = "\\\\?\\pipe\\cosmo\\";
+
+static textwindows size_t UintToChar16Array(char16_t *a, uint64_t i) {
+  size_t j = 0;
+  do {
+    a[j++] = i % 10 + '0';
+    i /= 10;
+  } while (i > 0);
+  a[j] = 0;
+  reverse(a, j);
+  return j;
+}
+
+textwindows char16_t *CreatePipeName(char16_t *a) {
+  static long x;
+  unsigned i;
+  for (i = 0; kPipeNamePrefix[i]; ++i) a[i] = kPipeNamePrefix[i];
+  i += UintToChar16Array(a + i, GetCurrentProcessId());
+  a[i++] = u'-';
+  i += UintToChar16Array(a + i, GetCurrentProcessId());
+  a[i++] = u'-';
+  i += UintToChar16Array(a + i, x++);
+  a[i] = u'\0';
+  return a;
+}