Define HTTP_SERVER_POLL_CAPACITY and HTTP_CLIENT_POLL_CAPACITY so that users can easily allocate poll arrays of the right size

src/client.h

@@ -5,6 +5,11 @@
 #define HTTP_CLIENT_CAPACITY (1<<7)
 #endif
 
+// Maximum number of descriptors the client will want
+// to wait on. It's one per connection plus the wakeup
+// self-pipe.
+#define HTTP_CLIENT_POLL_CAPACITY (HTTP_CLIENT_CAPACITY+1)
+
 typedef enum {
     HTTP_CLIENT_CONN_FREE,
     HTTP_CLIENT_CONN_WAIT_LINE,

src/server.h

@@ -5,6 +5,11 @@
 #define HTTP_SERVER_CAPACITY (1<<9)
 #endif
 
+// Maximum number of descriptors the server will want
+// to wait on. It's one per connection plus two for the
+// TCP and TLS listener, plus one for the wakeup self-pipe.
+#define HTTP_SERVER_POLL_CAPACITY (HTTP_SERVER_CAPACITY+3)
+
 typedef enum {
 
     // This struct is unused