Log Message:
Update to 1.7a provided by Leonardo Taccari in PR 49918.

MuPDF 1.7a (2015-05-07)
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The 1.7a version is a bugfix release. Bug fixes:
* Fixed bug that allocated too much memory when packing paths.
* Fixed EPUB font scaling bug.
* Fixed EPUB file type handling in viewers.
* Improved tolerance for broken and unsupported CSS.

New features:
* Added -z option to mutool clean.