Header fixes:

* Do not include system headers in shared files (stdlib.h).
* Don't include lcd.h only once in each driver.
* Remove some unnecessary headers from driver (e.g. syslog.h)
* Include <poll.h> instead of <sys/poll.h>
* Spelling fixes.

clients/lcdexec/menu.c

@@ -15,6 +15,7 @@
 #include <unistd.h>
 #include <string.h>
 #include <strings.h>
+#include <stdlib.h>
 
 #include "shared/report.h"
 #include "shared/configfile.h"