tests/FILEFORMAT: mention how to use <fileN> and <stripfileN> too

have a text/binary difference.

Variables are substituted as in the <command> section.

</file>

<file1>

1 to 4 can be appended to 'file' to compare more files.

</file1>

<file2>

</file2>

<file3>

</file3>

<file4>

</file4>

<stripfile>

One perl op per line that operates on the output file or stdout before being

compared with what is stored in the test file. This is pretty

advanced. Example: "s/^EPRT .*/EPRT stripped/"

</stripfile>

<stripfile1>

1 to 4 can be appended to 'stripfile' to strip the correspending <fileN>

content

</stripfile1>

<stripfile2>

</stripfile2>

<stripfile3>

</stripfile3>

<stripfile4>

</stripfile4>

<upload>

the contents of the upload data curl should have sent

</upload>