Fix some glitches in redbean

This change includes a fix to Fetch() where an out of bounds memory read
could happen, when the reverse proxied endpoint omits the content-length
header. This caused a bunch of NUL chars to appear on TurfWar's /statusz
since it wouldn't actually overrun the buffer, and if it did it would've
been caught by MODE=asan builds.

tool/net/fetch.inc

@@ -364,7 +364,7 @@ static int LuaFetch(lua_State *L) {
         break;
       case kHttpClientStateBody:
         if (!g) {
-          paylen = inbuf.n;
+          paylen = inbuf.n - hdrsize;
           goto Finished;
         }
         break;