libxml2 security update

[2.7.6-20.0.1]

• Update doc/redhat.gif in tarball
• Add libxml2-oracle-enterprise.patch and update logos in tarball
  [2.7.6-20.1]
• Fix a series of CVEs (rhbz#1286495)
• CVE-2015-7941 Cleanup conditional section error handling
• CVE-2015-8317 Fail parsing early on if encoding conversion failed
• CVE-2015-7942 Another variation of overflow in Conditional sections
• CVE-2015-7942 Fix an error in previous Conditional section patch
• Fix parsing short unclosed comment uninitialized access
• CVE-2015-7498 Avoid processing entities after encoding conversion failures
• CVE-2015-7497 Avoid an heap buffer overflow in xmlDictComputeFastQKey
• CVE-2015-5312 Another entity expansion issue
• CVE-2015-7499 Add xmlHaltParser() to stop the parser
• CVE-2015-7499 Detect incoherency on GROW
• CVE-2015-7500 Fix memory access error due to incorrect entities boundaries
• CVE-2015-8242 Buffer overead with HTML parser in push mode
• Libxml violates the zlib interface and crashes