Remove variadic arguments from logger callback (#435) (#480)

docs/2_1_common_api.adoc

@@ -352,7 +352,7 @@ If `logger` is called with `status = fmi3OK`, then the message is a pure informa
 The meaning of `category` is defined by the modeling environment that generated the FMU.
 Depending on this modeling environment, none, some or all allowed values of `category` for this FMU are defined in the `modelDescription.xml` file via element `<fmiModelDescription><LogCategories>`, see section 2.2.4.
 Only messages are provided by function `logger` that have a category according to a call to `fmi3SetDebugLogging` (see below).
-Argument `message` is provided in the same way and with the same format control as in function `printf` from the C standard library.
+Argument `message` is a string that contains the message.
 _[Typically, this function prints the message and stores it optionally in a log file.]_
 +
 All string-valued arguments passed by the FMU to the `logger` may be deallocated by the FMU directly after function `logger` returns.

headers/fmi3FunctionTypes.h

@@ -106,7 +106,7 @@ typedef void  (*fmi3CallbackLogger)         (fmi3ComponentEnvironment componentE
                                              fmi3String instanceName,
                                              fmi3Status status,
                                              fmi3String category,
-                                             fmi3String message, ...);
+                                             fmi3String message);
 typedef void* (*fmi3CallbackAllocateMemory) (fmi3ComponentEnvironment componentEnvironment,
                                              size_t nobj,
                                              size_t size);