libxml2: remove HTML support

Disabling HTML support from libxml2 as it has vulnerabilities
(see bug) and is not used in Android.

(cherry picked from commit edb5870767fed8712a9b77ef34097209b61ab2db)
Bug: 27338391

Change-Id: Ib901550b785c8150c8470a3f73d1b3cb2ba70d21
diff --git a/Android.mk b/Android.mk
index 6ec8012..07c7b37 100644
--- a/Android.mk
+++ b/Android.mk
@@ -37,7 +37,7 @@
 # We deliberately exclude nanoftp.c and nanohttp.c, the trio library, and zlib.
 common_SRC_FILES := SAX.c entities.c encoding.c error.c \
         parserInternals.c parser.c tree.c hash.c list.c xmlIO.c \
-        xmlmemory.c uri.c valid.c xlink.c HTMLparser.c HTMLtree.c \
+        xmlmemory.c uri.c valid.c xlink.c \
         debugXML.c xpath.c xpointer.c xinclude.c \
         DOCBparser.c catalog.c globals.c threads.c c14n.c xmlstring.c \
         buf.c xmlregexp.c xmlschemas.c xmlschemastypes.c xmlunicode.c \