Base/App: fix warnings from code analysers:

* convert old-style-casts to explicit C++ casts where possible
* make some implicit conversions explicit

src/Base/Quantity.cpp

@@ -438,12 +438,21 @@ double num_change(char* yytext,char dez_delim,char grp_delim)
     return ret_val;
 }
 
+#if defined(__clang__)
+# pragma clang diagnostic push
+# pragma clang diagnostic ignored "-Wmissing-noreturn"
+#endif
+
 // error func
 void Quantity_yyerror(char *errorinfo)
 {
     throw Base::ParserError(errorinfo);
 }
 
+#if defined(__clang__)
+# pragma clang diagnostic pop
+#endif
+
 
 // for VC9 (isatty and fileno not supported anymore)
 //#ifdef _MSC_VER