Fix docblock parsing rule.

We first require that the first character after a /// not be a newline,
in addition to it not being another /. Then we make the whole contents
of the line optional, so we can handle empty lines.

Engine/source/console/CMDscan.l

@@ -105,7 +105,7 @@ HEXDIGIT [a-fA-F0-9]
 %%
          ;
 {SPACE}+ { }
-("///"[^/][^\n\r]*[\n\r]*)+ { return(Sc_ScanDocBlock()); }
+("///"([^/\n\r][^\n\r]*)?[\n\r]+)+ { return(Sc_ScanDocBlock()); }
 "//"[^\n\r]*   ;
 [\r]        ;
 [\n]        {lineIndex++;}