BOOST_BINARY: operator '##' produced the invalid token ')END_BIT'

I'm using [vbcc](http://sun.hasenbraten.de/vbcc/), a C cross-compiler, targeting Amiga Kickstart 1.3.

The line
```C
custom.dmacon = BOOST_BINARY_U(0000000000000011);
```
produces the following error:
```
> custom.dmacon = BOOST_BINARY_U(0000000000000011)
error 276 in line 96 of "src\main.c": operator '##' produced the invalid token ')END_BIT'
```

Reproduce the failure in src\main.c at line 96 with vbcc targeting Amiga Kickstart 1.3, using the shown BOOST_BINARY_U invocation. Inspect the BOOST_BINARY_U macro expansion and preprocessing around the call; done means the expansion no longer produces the invalid ')END_BIT' token and the source compiles.

Written by the indexing model from the issue text.