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

third_party/mbedtls/ctr_drbg.c

@@ -431,7 +431,7 @@ static size_t good_nonce_len( size_t entropy_len )
 int mbedtls_ctr_drbg_seed( mbedtls_ctr_drbg_context *ctx,
                            int (*f_entropy)(void *, unsigned char *, size_t),
                            void *p_entropy,
-                           const unsigned char *custom,
+                           const void *custom,
                            size_t len )
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;