Fix bdiff test failures on AIX.
The test fails when, in the call to calloc(), the number of elements (bn)
is 0. In that case, calloc() on AIX will return NULL, while the code expects
a valid heap pointer. Both results are permissible under C99, Unix98 etc.
Work around by ensuring that at least 1 element is requested.
workaround for raw_input() on Windows
Since change
a3fe91b4f6eb, Mercurial has set_binary() on stdin, stdout, and stderr.
On Windows, this had the side effect of causing raw_input() to emit trailing carriage
returns on it's returned strings. This was causing web authentication problems.