Generate more detailed error messages.

Eliminate duplicate definition (in input plugin and decoder plugin).

Let the caller decide whether to strip.  Only remove \n and \r
(end-of-line markers).

Look at the buffer first, before trying to read from the file.  This
reduces overhead because we don't refill the buffer after every line.

Revert to the old API before commit e9e55b08, removing unnecessary
bloat.

Checking "!open" did not work with the NFS plugin because that plugin
does not close the file automatically, unlike CURL.

This reverts commit 966c4244.

The commit was bad, because the bug was really in
NfsInputStream::DoRead(); see previous commit.

Avoids off-by-one bug and obsoletes the bug fix in commit 966c4244

More robust and cancellable.

May cause assertion failure.

New base class for other InputStream implementations that run in the
I/O thread.

Fixes assertion failure.

Remove the "whence" parameter that is not actually necessary, and only
complicates the InputStream implementations.

Allow compiling test programs with only selected plugins.

Caused by commit 0b4fa41a

Make attributes const, don't allow partial initialization.
Instantiate the CdioParanoiaInputStream object at the end of
input_cdio_open().