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Using macro__ARM_WCHAR_NO_IO to disable FILE declaration and wide I/O function prototypes

In strict C/C++ mode, the header files wchar.h and cwchar do not declare the FILE type. You can also define the macro __ARM_WCHAR_NO_IO to cause these header files not to declare FILE or the wide I/O function prototypes.

Declaring the FILE type can lead to better consistency in debug information.