Add HTTP/HTTPS Fetch() API to redbean

You can now say the following in your redbean Lua code:

    status,headers,payload = Fetch("https://foo.example")

The following Lua APIs have been introduced:

  - Fetch(str) → str,{str:str},str
  - GetHttpReason(int) → str
  - GetHttpReason(int) → str
  - ProgramSslFetchVerify(bool)
  - ProgramSslClientVerify(bool)

The following flags have been introduced:

  - `-j` enables client SSL verification
  - `-k` disables Fetch() SSL verification
  - `-t INT` may now be passed a negative value for keepalive

Lua exceptions now invoke Cosmopolitan's garbage collector when
unwinding the stack. So it's now safe to use _gc() w/ Lua 𝔱𝔥𝔯𝔬𝔴

See #97

tool/net/counters.inc

@@ -84,12 +84,14 @@ C(sslcantciphers)
 C(sslhandshakefails)
 C(sslhandshakes)
 C(sslnociphers)
+C(sslnoclientcert)
 C(sslnoversion)
 C(sslshakemacs)
 C(ssltimeouts)
 C(sslunknownca)
 C(sslunknowncert)
 C(sslupgrades)
+C(sslverifyfailed)
 C(statfails)
 C(staticrequests)
 C(stats)