Bug 695566 and 695567: Update MuJS submodule.
xml: Don't emit empty text nodes between tags when preserving whitespace.
xml: Optimize creation of really long lists by keeping a tail pointer.
xml: Make accessors NULL-resistant. Add fz_xml_find functions.

Find the first sibling, next sibling or first child matching tag name.
Don't always trim the buffer when calling fz_read_all.

Many instances just use the data and free it, so reallocing to shrink
is a waste of time. Other instances need to append a terminating zero,
such as the XML and CSS parsers.
Add convenience fz_read_file function.

Read the contents of a file into a fz_buffer in one go.
Fix off-by-one in fz_write_buffer_byte.
Add ZIP file and directory reading module.
xps: Use ZIP archive module.
cbz: Use ZIP archive module.
Add dirname and cleanname path manipulation functions.
Add fz_layout_document function.
Don't automatically trim buffer during fz_keep_buffer.

It's surprising and may cause unexpected effects for code that may have
saved pointers to the underlying data in read only buffers, such as
fz_new_image_from_buffer.
Fix leak of directory string in fz_archive.
Update MuJS to latest.