Idempotent build: configure.php

[alfsb]

This PR does a few clean ups, creates functions for consistent loading and reloading of manual XML saves all intermediary and final XML on temp/, and changes error reporting.

The reloading of XML is necessary to validation and file/line/column information works correctly, The error message causes build failures like this:

 Opening and ending tag mismatch: para line 19 and par

to be reported like this:

[FATAL  26:10] Opening and ending tag mismatch: para line 19 and par
[FATAL  27:1] chunk is not well balanced
[FATAL en/appendices/migration56/incompatible.xml 87:42] Entity 'migration56.openssl.peer-verification' failed to parse
[FATAL en/appendices/migration56/incompatible.xml 144:1] chunk is not well balanced
[FATAL en/appendices/migration56.xml 24:39] Entity 'appendices.migration56.incompatible' failed to parse
[FATAL en/appendices/migration56.xml 54:1] chunk is not well balanced
[FATAL zpr-doc-base/manual.xml 443:27] Entity 'appendices.migration56' failed to parse

That's right. We now have contextual, call stack-like error messages for errors inside of entities. How nice is this?

[Girgias]

This is pretty cool!

[alfsb]

Merged. The CI errors are unrelated as far I can see.

git mv reference/spl/countable.xml to language/predefined/countable.xml and update the entity reference at end of XML.