Add libesphttpd to extras and supporting example (#458)

* libesphttpd: added extras and example

* Added "heatshrink" as a submodule

* Updated libesphttpd

* Updated libesphttpd

* Trying to fix the commit id

* Updated libesphttpd

* Added zlib1g-dev package

* Use native gcc to build mkespfsimage and mkupgimg

* Added NS and GW for DHCP server configuration

examples/esphttpd/cgi.c

@@ -0,0 +1,81 @@
+/*
+Some random cgi routines. Used in the LED example and the page that returns the entire
+flash as a binary. Also handles the hit counter on the main page.
+*/
+
+/*
+ * ----------------------------------------------------------------------------
+ * "THE BEER-WARE LICENSE" (Revision 42):
+ * Jeroen Domburg <jeroen@spritesmods.com> wrote this file. As long as you retain 
+ * this notice you can do whatever you want with this stuff. If we meet some day, 
+ * and you think this stuff is worth it, you can buy me a beer in return. 
+ * ----------------------------------------------------------------------------
+ */
+
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+
+#include <espressif/esp_common.h>
+
+#include "cgi.h"
+#include "io.h"
+
+
+//cause I can't be bothered to write an ioGetLed()
+static char currLedState=0;
+
+//Cgi that turns the LED on or off according to the 'led' param in the POST data
+int ICACHE_FLASH_ATTR cgiLed(HttpdConnData *connData) {
+	int len;
+	char buff[1024];
+	
+	if (connData->conn==NULL) {
+		//Connection aborted. Clean up.
+		return HTTPD_CGI_DONE;
+	}
+
+	len=httpdFindArg(connData->post->buff, "led", buff, sizeof(buff));
+	if (len!=0) {
+		currLedState=atoi(buff);
+		ioLed(currLedState);
+	}
+
+	httpdRedirect(connData, "led.tpl");
+	return HTTPD_CGI_DONE;
+}
+
+
+
+//Template code for the led page.
+int ICACHE_FLASH_ATTR tplLed(HttpdConnData *connData, char *token, void **arg) {
+	char buff[128];
+	if (token==NULL) return HTTPD_CGI_DONE;
+
+	strcpy(buff, "Unknown");
+	if (strcmp(token, "ledstate")==0) {
+		if (currLedState) {
+			strcpy(buff, "on");
+		} else {
+			strcpy(buff, "off");
+		}
+	}
+	httpdSend(connData, buff, -1);
+	return HTTPD_CGI_DONE;
+}
+
+static int hitCounter=0;
+
+//Template code for the counter on the index page.
+int ICACHE_FLASH_ATTR tplCounter(HttpdConnData *connData, char *token, void **arg) {
+	char buff[128];
+	if (token==NULL) return HTTPD_CGI_DONE;
+
+	if (strcmp(token, "counter")==0) {
+		hitCounter++;
+		sprintf(buff, "%d", hitCounter);
+	}
+	httpdSend(connData, buff, -1);
+	return HTTPD_CGI_DONE;
+}