Add utf-8 escape for encode#4

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kindy wants to merge 3 commits intompx:masterfrom

Commits on May 18, 2012

Add encode_escape_utf8() method for escape utf8 to \uxxxx
kindy
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Commits on May 23, 2012

Init encode_escape_utf8 in config init
kindy
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Commits on Dec 13, 2012

add manual for encode_escape_utf8
kindy
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