Prevent doxygen from including the C API in the C++ API again

Author: tstenner

doc/Doxyfile_API

@@ -18,6 +18,10 @@ EXCLUDE_SYMBOLS        =  lslboost
 SOURCE_BROWSER         = YES
 CLANG_ASSISTED_PARSING = NO
 CLANG_OPTIONS          = -I../lslboost
+MACRO_EXPANSION        = YES
+EXPAND_ONLY_PREDEF     = YES
+ENABLE_PREPROCESSING   = YES
+PREDEFINED             = LIBLSL_C_API DOXYGEN_SHOULD_SKIP_THIS
 ALPHABETICAL_INDEX     = NO
 HTML_DYNAMIC_SECTIONS  = YES
 GENERATE_TREEVIEW      = YES

include/lsl_cpp.h

@@ -23,7 +23,9 @@
 #include <stdexcept>
 
 namespace lsl {
+#ifndef DOXYGEN_SHOULD_SKIP_THIS
    #include "lsl_c.h"
+#endif
 
     /**
     * Constant to indicate that a stream has variable sampling rate.