C Clubby refactoring

Complete rewrite of the C Clubby implementation: it is now modeled after
the Go implementation, with a slight difference that codec and channel
are the same object (something we should probably do in Go as well, as
we only have a single type of channel so far, which is used with all
types of codecs).

This implementation also comes with a new external API,
which is hopefully cleaner and easier to use (see mg_clubby.h).

In this PR I am not adding any new types of channels, but a UART channel
as well as websocket listener channel will be added after this lands.

PUBLISHED_FROM=d545d4bb6434e2a02ad159f9e4b64e594a4797e7

mongoose.c

@@ -1064,6 +1064,7 @@ void mbuf_remove(struct mbuf *mb, size_t n) {
 
 /* Amalgamated: #include "common/mg_str.h" */
 
+#include <stdlib.h>
 #include <string.h>
 
 int mg_ncasecmp(const char *s1, const char *s2, size_t len);
@@ -1096,6 +1097,30 @@ int mg_vcasecmp(const struct mg_str *str1, const char *str2) {
   }
   return r;
 }
+
+struct mg_str mg_strdup(const struct mg_str s) {
+  struct mg_str r = {NULL, 0};
+  if (s.len > 0 && s.p != NULL) {
+    r.p = (char *) malloc(s.len);
+    if (r.p != NULL) {
+      memcpy((char *) r.p, s.p, s.len);
+      r.len = s.len;
+    }
+  }
+  return r;
+}
+
+int mg_strcmp(const struct mg_str str1, const struct mg_str str2) {
+  size_t i = 0;
+  while (i < str1.len && i < str2.len) {
+    if (str1.p[i] < str2.p[i]) return -1;
+    if (str1.p[i] > str2.p[i]) return 1;
+    i++;
+  }
+  if (i < str1.len) return 1;
+  if (i < str2.len) return -1;
+  return 0;
+}
 #ifdef MG_MODULE_LINES
 #line 1 "./src/../../common/sha1.c"
 #endif

mongoose.h

@@ -811,6 +811,9 @@ int mg_vcmp(const struct mg_str *str2, const char *str1);
  */
 int mg_vcasecmp(const struct mg_str *str2, const char *str1);
 
+struct mg_str mg_strdup(const struct mg_str s);
+int mg_strcmp(const struct mg_str str1, const struct mg_str str2);
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */