* test/utf16bebom.xml: regression test showed that this test case was
broken but previous behaviour would not detect it !
* parser.c: fix 566012 for the push mode of the parser, tricky !
* test/ebcdic_566012.xml result//ebcdic_566012.xml*: add the test to the
regression suite
* encoding.c, include/libxml/encoding.h: Enhanced the handling of UTF-16,
UTF-16LE and UTF-16BE encodings. Now UTF-16 output is handled internally
by default, with proper BOM and UTF-16LE encoding. Native UTF-16LE and
UTF-16BE encoding will not generate a BOM on output, and will be
automatically recognized on input.
* test/utf16lebom.xml, test/utf16bebom.xml, result/utf16?ebom*: added
regression tests for above.
