* Check for backslash characters before the start of the new data
With BOOST_WAVE_BSIZE set to 40, test t_5_002 fails because a newline appears exactly at the beginning of a newly
fetched buffer, and a backslash is at the end of the previous one. In that case the escaped newline
was not detected. This change will also consider three unprocessed bytes of input data, if available,
prior to the new data, which is enough to detect a trigraph backslash.
* Improve data range check for backslash newline
The existing check considered the space required for a trigraph backslash, but not for the following LF (or CRLF) before testing for them. With BOOST_WAVE_BSIZE set to 98 this caused a segfault in t_5_001.
Use correct string constructor for non-null-terminated range (#204)
There is no guarantee (indeed, it is unlikely) that data within the
scanner buffer will be null terminated, and so the constructor that
accepts a pointer and a count is appropriate.
