Use strict C function prototypes

This fixes warnings when compiling with `-Wstrict-prototypes`.

Functions with empty parameter lists behave differently in C and C++:
- void func() in C is same as void func(...) in C++.
- void func() in C++ is same as void func(void) in C.

tools/make_libcef_dll_dylib_impl.py

@@ -52,7 +52,7 @@ def make_libcef_dll_dylib_impl_parts(name, retval, args):
 
 def make_libcef_dll_dylib_impl_func(func):
   name = func.get_capi_name()
-  parts = func.get_capi_parts([])
+  parts = func.get_capi_parts([], True)
   retval = parts['retval']
   args = parts['args']
   return make_libcef_dll_dylib_impl_parts(name, retval, args)