Updated pugixml to 1.8.1.

1.8.1

This is a re-release of v1.8 with fixed timestamps for files in .tar.gz

1.8

Maintenance release.

Release highlights:

    Added parse_embed_pcdata parsing mode to reduce memory consumption for some documents
    Added Latin-1 auto-detection support
    When printing empty elements, a space is no longer added before / in format_raw mode
    Fix compilation issues for Borland C++ 5.4 and some distributions of MinGW 3.8

(wiz)