Log Message:
libxml2: updated to 2.9.9

v2.9.9:
Security:
CVE-2018-9251 CVE-2018-14567 Fix infinite loop in LZMA decompression
CVE-2018-14404 Fix nullptr deref with XPath logic ops

Documentation:
reader: Fix documentation comment

Portability:
Fix MSVC build with lzma
Variables need 'extern' in static lib on Cygwin
Really declare dllexport/dllimport for Cygwin
Merge branch 'patch-2' into 'master'
Change dir to $THEDIR after ACLOCAL_PATH check autoreconf creates aclocal.m4 in \ 
$srcdir
Improve error message if pkg.m4 couldn't be found
NaN and Inf fixes for pre-C99 compilers

Bug Fixes:
Revert "Support xmlTextReaderNextSibling w/o preparsed doc"
Fix building relative URIs
Problem with data in interleave in RelaxNG validation
Fix memory leak in xmlSwitchInputEncodingInt error path
Set doc on element obtained from freeElems
Fix HTML serialization with UTF-8 encoding
Use actual doc in xmlTextReaderRead*Xml
Unlink node before freeing it in xmlSAX2StartElement
Check return value of nodePush in xmlSAX2StartElement
Free input buffer in xmlHaltParser
Reset HTML parser input pointers on encoding failure
Don't run icu_parse_test if EUC-JP is unsupported
Fix xmlSchemaValidCtxtPtr reuse memory leak
Fix xmlTextReaderNext with preparsed document
Remove stray character from comment
Remove a misleading line from xmlCharEncOutput
HTML noscript should not close p
Don't change context node in xmlXPathRoot
Stop using XPATH_OP_RESET
Revert "Change calls to xmlCharEncInput to set flush false"

Improvements:
Fix "Problem with data in interleave in RelaxNG validation"
cleanup: remove some unreachable code
add --relative to testURI
Remove redefined starts and defines inside include elements
Allow choice within choice in nameClass in RELAX NG
Look inside divs for starts and defines inside include
Add compile and libxml2-config.cmake to .gitignore
Stop using doc->charset outside parser code
Add newlines to 'xmllint --xpath' output
Don't include SAX.h from globals.h
Support xmlTextReaderNextSibling w/o preparsed doc
Don't instruct user to run make when autogen.sh failed
Run Travis ASan tests with "sudo: required"
Improve restoring of context size and position
Simplify and harden nodeset filtering
Avoid unnecessary backups of the context node
Fix inconsistency in xmlXPathIsInf