Crangler: silence lexer build warnings

Some versions of compilers (combined with particular flex variants) will
result in compiler warnings that we already silence for various others
lexers.

Author: tautschnig

src/crangler/scanner.l

@@ -54,6 +54,16 @@ PreprocessorDirective           {PreprocessorStart}[^\r\n]*
 static int isatty(int) { return 0; }
 #endif
 
+#if defined _MSC_VER
+// signed/unsigned mismatch
+#pragma warning(disable:4365)
+// macro re-definition: flex conditonally defines INT32_MAX et al. and thus
+// they are set before library headers get to define them
+#pragma warning(disable:4005)
+#endif
+
+#include <util/pragma_wsign_compare.def>
+#include <util/pragma_wnull_conversion.def>
 #include <util/pragma_wdeprecated_register.def>
 
 #include <set>