pt_BR.ISO8859-1/articles/filtering-bridges: New pt_BR translation into .po format

• content synchronized with en_US document (rev 44681)
• article.xml converted to .po
• .po file was translated to pt_BR
• .po and .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