[all] use explicit void parameter lists

This makes it a compile-time error to call a function that semantically
takes no parameters with a nonzero number of arguments.

Previously, such code would still compile, but risk blowing up the stack
if a compiler chose to use something other than caller-cleanup calling
conventions.

common/src/option.c

@@ -210,7 +210,7 @@ bool option_register(struct Option options[])
   return true;
 };
 
-void option_free()
+void option_free(void)
 {
   for(int i = 0; i < state.oCount; ++i)
   {
@@ -520,7 +520,7 @@ exit:
   return result;
 }
 
-bool option_validate()
+bool option_validate(void)
 {
   if (state.doHelp)
   {
@@ -571,7 +571,7 @@ bool option_validate()
   return ok;
 }
 
-void option_print()
+void option_print(void)
 {
   printf(
     "The following is a complete list of options accepted by this application\n\n"