Disable various unused libxml features: catalogs, DocBook, legacy APIs, etc.

third_party/libxml/BUILD.gn

Index: third_party/libxml/BUILD.gn
diff --git a/third_party/libxml/BUILD.gn b/third_party/libxml/BUILD.gn
index 147455b544aaae978d8d94efc680b34b979fd47a..41c0fa716c4b44aa49cf0ad61aa123fa1c43d215 100644
--- a/third_party/libxml/BUILD.gn
+++ b/third_party/libxml/BUILD.gn
@@ -78,17 +78,17 @@ static_library("libxml") {
     "linux/include/libxml/xmlversion.h",
     "mac/config.h",
     "mac/include/libxml/xmlversion.h",
-    "src/DOCBparser.c",
+    #"src/DOCBparser.c",
     "src/HTMLparser.c",
     "src/HTMLtree.c",
-    "src/SAX.c",
+    #"src/SAX.c",
     "src/SAX2.c",
     "src/buf.c",
     "src/buf.h",
-    "src/c14n.c",
-    "src/catalog.c",
+    #"src/c14n.c",
+    #"src/catalog.c",
     "src/chvalid.c",
-    "src/debugXML.c",
+    #"src/debugXML.c",
     "src/dict.c",
     "src/elfgcchack.h",
     "src/enc.h",
@@ -145,21 +145,20 @@ static_library("libxml") {
     "src/include/libxml/xpointer.h",
     "src/include/win32config.h",
     "src/include/wsockcompat.h",
-    "src/legacy.c",
+    #"src/legacy.c",
     "src/libxml.h",
     "src/list.c",
     "src/parser.c",
     "src/parserInternals.c",
     "src/pattern.c",
-    "src/relaxng.c",
+    #"src/relaxng.c",
     "src/save.h",
-    "src/schematron.c",
+    #"src/schematron.c",
     "src/threads.c",
     "src/timsort.h",
     "src/tree.c",
     "src/triodef.h",
     "src/trionan.h",
-
     #"src/trio.c",
     #"src/trio.h",
     #"src/triodef.h",
@@ -170,22 +169,21 @@ static_library("libxml") {
     #"src/triostr.h",
     "src/uri.c",
     "src/valid.c",
-    "src/xinclude.c",
-    "src/xlink.c",
+    #"src/xinclude.c",
+    #"src/xlink.c",
     "src/xmlIO.c",
     "src/xmlmemory.c",
-    "src/xmlmodule.c",
+    #"src/xmlmodule.c",
     "src/xmlreader.c",
-    "src/xmlregexp.c",
+    #"src/xmlregexp.c",
     "src/xmlsave.c",
-    "src/xmlschemas.c",
-    "src/xmlschemastypes.c",
+    #"src/xmlschemas.c",
+    #"src/xmlschemastypes.c",
     "src/xmlstring.c",
     "src/xmlunicode.c",
     "src/xmlwriter.c",
     "src/xpath.c",
-    "src/xpointer.c",
-
+    #"src/xpointer.c",
     #"src/xzlib.c",
     "src/xzlib.h",
     "win32/config.h",