Clean up various C source and headers to appease -Wstrict-prototypes

In C, func() is a function taking an unspecified number of arguments,
vs func(void) a function taking no arguments. In C++ both forms indicate
"no arguments."

Update these headers to use the (void) form, which is correct in both
languages and avoids complaints when -Wstrict-prototypes is specified.

src/common/pico_base/include/pico/assert.h

@@ -36,7 +36,7 @@ extern "C" {
 #define hard_assert_if(x, test) ({if (PARAM_ASSERTIONS_ENABLED(x)) hard_assert(!(test));})
 
 #ifdef NDEBUG
-extern void hard_assertion_failure();
+extern void hard_assertion_failure(void);
 static inline void hard_assert(bool condition, ...) {
     if (!condition)
         hard_assertion_failure();