pt_BR.ISO8859-1/articles/freebsd-update-server: converted to .po

• content synchronized with en_US document (rev 51862)
• article.xml converted to .po
• .po file was translated to pt_BR
• pt_BR.po and article.xml file has been set to UTF-8 encoding
• information about volunteers who translated and/or revised the document was added to the header of the .po file

Approved by: gabor (mentor, implicit)
Obtained from: The FreeBSD Brazilian Portuguese Documentation Project