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

net/http/http.h

@@ -36,6 +36,11 @@
 #define kHttpStateLf1     10
 #define kHttpStateLf2     11
 
+#define kHttpClientStateHeaders      0
+#define kHttpClientStateBody         1
+#define kHttpClientStateBodyChunked  2
+#define kHttpClientStateBodyLengthed 3
+
 #define kHttpStateChunkStart   0
 #define kHttpStateChunkSize    1
 #define kHttpStateChunkExt     2