Honor DNS server from DHCP

PUBLISHED_FROM=10772301ef115c31ada3521ff4235c33a421b782

docs/c-api/net.h/struct_mg_connect_opts.md

@@ -8,6 +8,7 @@ signature: |
     unsigned int flags;        /* Extra connection flags */
     const char **error_string; /* Placeholder for the error string */
     struct mg_iface *iface;    /* Interface instance */
+    const char *nameserver;    /* DNS server to use, NULL for default */
   #if MG_ENABLE_SSL
     /*
      * SSL settings.

docs/c-api/net.h/struct_mg_mgr.md

@@ -17,6 +17,7 @@ signature: |
   #if MG_ENABLE_JAVASCRIPT
     struct v7 *v7;
   #endif
+    const char *nameserver; /* DNS server to use */
   };
 ---
 

docs/c-api/net.h/struct_mg_mgr_init_opts.md

@@ -7,6 +7,7 @@ signature: |
     const struct mg_iface_vtable *main_iface;
     int num_ifaces;
     const struct mg_iface_vtable **ifaces;
+    const char *nameserver;
   };
 ---
 

docs/c-api/resolv.h/intro.md

@@ -6,6 +6,7 @@ items:
   - { name: mg_resolve_async.md }
   - { name: mg_resolve_async_opt.md }
   - { name: mg_resolve_from_hosts_file.md }
+  - { name: mg_set_nameserver.md }
   - { name: struct_mg_resolve_async_opts.md }
 ---
 

docs/c-api/resolv.h/mg_set_nameserver.md

@@ -0,0 +1,10 @@
+---
+title: "mg_set_nameserver()"
+decl_name: "mg_set_nameserver"
+symbol_kind: "func"
+signature: |
+  void mg_set_nameserver(struct mg_mgr *mgr, const char *nameserver);
+---
+
+Set default DNS server 
+

docs/c-api/resolv.h/struct_mg_resolve_async_opts.md

@@ -4,7 +4,7 @@ decl_name: "struct mg_resolve_async_opts"
 symbol_kind: "struct"
 signature: |
   struct mg_resolve_async_opts {
-    const char *nameserver_url;
+    const char *nameserver;
     int max_retries;    /* defaults to 2 if zero */
     int timeout;        /* in seconds; defaults to 5 if zero */
     int accept_literal; /* pseudo-resolve literal ipv4 and ipv6 addrs */