Add more POSIX function stubs

Cosmopolitan currently doesn't support threads and it doesn't do
anything fancy in longjmp/setjmp so this change was simple to do

- localeconv
- _setjmp (same as setjmp)
- _longjmp (same as longjmp)
- strcoll (same as strcmp)
- flockfile (does nothing)
- funlockfile (does nothing)
- ftrylockfile (does nothing)

See #61

libc/unicode/localeconv.c

@@ -0,0 +1,51 @@
+/*-*- 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/limits.h"
+#include "libc/unicode/unicode.h"
+
+static const struct lconv kLocaleConv = {
+    .decimal_point = ".",
+    .thousands_sep = "",
+    .grouping = "",
+    .int_curr_symbol = "",
+    .currency_symbol = "",
+    .mon_decimal_point = "",
+    .mon_thousands_sep = "",
+    .mon_grouping = "",
+    .positive_sign = "",
+    .negative_sign = "",
+    .int_frac_digits = CHAR_MAX,
+    .frac_digits = CHAR_MAX,
+    .p_cs_precedes = CHAR_MAX,
+    .p_sep_by_space = CHAR_MAX,
+    .n_cs_precedes = CHAR_MAX,
+    .n_sep_by_space = CHAR_MAX,
+    .p_sign_posn = CHAR_MAX,
+    .n_sign_posn = CHAR_MAX,
+    .int_p_cs_precedes = CHAR_MAX,
+    .int_p_sep_by_space = CHAR_MAX,
+    .int_n_cs_precedes = CHAR_MAX,
+    .int_n_sep_by_space = CHAR_MAX,
+    .int_p_sign_posn = CHAR_MAX,
+    .int_n_sign_posn = CHAR_MAX,
+};
+
+struct lconv *localeconv(void) {
+  return (/* unconst */ struct lconv *)&kLocaleConv;
+}