Rewrote the fix for r->end - r->start + 1 == ABS(s->len).  Previously
I modified s->len, but this breaks all sorts of other things, most
notably it makes s->conf - s->seq not equal to s->len, then leading to
broken confidence values and also to sequence insertion possibly
calling memmove off the end of the buffer. (Oddly not detected by
valgrind.)

We now fix the far more likely error; r->end instead.


git-svn-id: svn://svn.code.sf.net/p/staden/code/staden@3754 ba6f2710-ca9f-427c-89d3-5bf716dbc8e1