fix C compilation warning about function prototype in __SET_EXTERNAL

Example warning:
./POUS.c:1220:3: error: function declaration isn't a prototype [-Werror=strict-prototypes]
__SET_EXTERNAL(data__->,KN_AUT,,__GET_VAR(data__->KEY_AUT.STATE_OUT));
^
compilation terminated due to -Wfatal-errors.
cc1: all warnings being treated as errors

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Source: matiec

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Section: devel

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Priority: standard

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Maintainer: edouard <edouard.tisserant@gmail.com>

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Build-Depends: debhelper (>= 5), bison, flex

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Standards-Version: 3.7.2

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Package: matiec

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Architecture: any

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Depends: ${shlibs:Depends}, ${misc:Depends}

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Description: The IEC to ANSI-C compiler

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 Compiles ST/IL/SFC code into ANSI-C code