Improve Libc by making Python work even better

Actually Portable Python is now outperforming the Python binaries
that come bundled with Linux distros, at things like HTTP serving.
You can now have a fully featured Python install in just one .com
file that runs on six operating systems and is about 10mb in size.
With tuning, the tiniest is ~1mb. We've got most of the libraries
working, including pysqlite, and the repl now feels very pleasant.
The things you can't do quite yet are: threads and shared objects
but that can happen in the future, if the community falls in love
with this project and wants to see it developed further. Changes:

- Add siginterrupt()
- Add sqlite3 to Python
- Add issymlink() helper
- Make GetZipCdir() faster
- Add tgamma() and finite()
- Add legacy function lutimes()
- Add readlink() and realpath()
- Use heap allocations when appropriate
- Reorganize Python into two-stage build
- Save Lua / Python shell history to dotfile
- Integrate Python Lib embedding into linkage
- Make isregularfile() and isdirectory() go faster
- Make Python shell auto-completion work perfectly
- Make crash reports work better if changed directory
- Fix Python+NT open() / access() flag overflow error
- Disable Python tests relating to \N{LONG NAME} syntax
- Have Python REPL copyright() show all notice embeddings

The biggest technical challenge at the moment is working around
when Python tries to be too clever about filenames.

test/libc/tinymath/tgamma_test.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/math.h"
+#include "libc/runtime/gc.internal.h"
+#include "libc/testlib/testlib.h"
+#include "libc/x/x.h"
+
+TEST(tgamma, test) {
+  EXPECT_STREQ("inf", gc(xasprintf("%.15g", tgamma(0.))));
+  EXPECT_STREQ("-inf", gc(xasprintf("%.15g", tgamma(-0.))));
+  EXPECT_STREQ("9.51350769866873", gc(xasprintf("%.15g", tgamma(.1))));
+  EXPECT_STREQ("-10.6862870211932", gc(xasprintf("%.15g", tgamma(-.1))));
+  EXPECT_STREQ("1.77245385090552", gc(xasprintf("%.15g", tgamma(.5))));
+  EXPECT_STREQ("-3.54490770181103", gc(xasprintf("%.15g", tgamma(-.5))));
+  EXPECT_STREQ("1", gc(xasprintf("%.15g", tgamma(1.))));
+  EXPECT_TRUE(isnan(tgamma(-1.)));
+  EXPECT_STREQ("0.886226925452758", gc(xasprintf("%.15g", tgamma(1.5))));
+  EXPECT_STREQ("2.36327180120735", gc(xasprintf("%.15g", tgamma(-1.5))));
+  EXPECT_STREQ("1", gc(xasprintf("%.15g", tgamma(2.))));
+  EXPECT_TRUE(isnan(tgamma(NAN)));
+  EXPECT_TRUE(isnan(tgamma(-NAN)));
+  EXPECT_STREQ("inf", gc(xasprintf("%.15g", tgamma(INFINITY))));
+  EXPECT_TRUE(isnan(tgamma(-INFINITY)));
+  EXPECT_STREQ("4.49423283715579e+307",
+               gc(xasprintf("%.15g", tgamma(__DBL_MIN__))));
+  EXPECT_STREQ("inf", gc(xasprintf("%.15g", tgamma(__DBL_MAX__))));
+  EXPECT_STREQ("4.5035996273705e+15",
+               gc(xasprintf("%.14g", tgamma(-1.0000000000000002))));
+  EXPECT_STREQ("-47453133.3893415",
+               gc(xasprintf("%.15g", tgamma(-2.1073424255447e-08))));
+}