Fix #224

Contains the fixes of @Whimse applied to the current develop branch together with changes in the compiler and dpp preprocessor that validate the declarations for the number of fixed function arguments in symbols_list.h. The necessary dispatch methods needed for iOS are by default switched off, but can be turned on by supplying CFLAGS = -DECL_C_COMPATIBLE_VARIADIC_DISPATCH.

@polos, would it be possible to test this branch on iOS? I don't have a device to do this and can only confirm that it works for x86_64. Could you also post the commands that you used to build ECL for iOS and the cross_config file? Then we can add this to the documentation and officially support iOS in the upcoming release.