Adding double quote as illegal character in Windows file names,

...thanks to ilor for pointing this out.

src/dialogs.cpp

@@ -224,7 +224,7 @@ bool is_illegal_file_char(char c)
 {
 	return c == '/' || c == '\\' || c == ':'
  	#ifdef WIN32
-	|| c == '?' || c == '|' || c == '<' || c == '>' || c == '*'
+	|| c == '?' || c == '|' || c == '<' || c == '>' || c == '*' || c == '"'
 	#endif
 	;
 }