Add parse_trim_pcdata parse option.

git-svn-id: https://pugixml.googlecode.com/svn/trunk@987 99668b35-9821-0410-8761-19e4c4f06640
tests: Add tests for parse_trim_pcdata.

git-svn-id: https://pugixml.googlecode.com/svn/trunk@988 99668b35-9821-0410-8761-19e4c4f06640
docs: Add parse_trim_pcdata documentation, change release date to March 1st.

git-svn-id: https://pugixml.googlecode.com/svn/trunk@989 99668b35-9821-0410-8761-19e4c4f06640