Reenable xz support by default

For https://bugzilla.gnome.org/show_bug.cgi?id=757466

problem was introduced by commit f3f86ff465c92c79f834d7b981f3c7274a8bb5c8
for https://bugzilla.gnome.org/show_bug.cgi?id=711026
diff --git a/configure.ac b/configure.ac
index 14ac0a8..48e0577 100644
--- a/configure.ac
+++ b/configure.ac
@@ -445,6 +445,9 @@
                 fi],
                 [have_liblzma=no])
 	     LDFLAGS="${SAVE_LDFLAGS}"])
+    else
+	# we still need to check for lzma,h header
+	AC_CHECK_HEADERS([lzma.h])
     fi
 
     # Found the library via either method?
diff --git a/xmlIO.c b/xmlIO.c
index e628ab0..8b13184 100644
--- a/xmlIO.c
+++ b/xmlIO.c
@@ -1334,7 +1334,7 @@
 }
 #endif /* HAVE_ZLIB_H */
 
-#ifdef HAVE_LZMA_H
+#ifdef LIBXML_LZMA_ENABLED
 /************************************************************************
  *									*
  *		I/O for compressed file accesses			*
@@ -1451,7 +1451,7 @@
     if (ret < 0) xmlIOErr(0, "xzclose()");
     return(ret);
 }
-#endif /* HAVE_LZMA_H */
+#endif /* LIBXML_LZMA_ENABLED */
 
 #ifdef LIBXML_HTTP_ENABLED
 /************************************************************************
@@ -2328,10 +2328,10 @@
     xmlRegisterInputCallbacks(xmlGzfileMatch, xmlGzfileOpen,
 	                      xmlGzfileRead, xmlGzfileClose);
 #endif /* HAVE_ZLIB_H */
-#ifdef HAVE_LZMA_H
+#ifdef LIBXML_LZMA_ENABLED
     xmlRegisterInputCallbacks(xmlXzfileMatch, xmlXzfileOpen,
 	                      xmlXzfileRead, xmlXzfileClose);
-#endif /* HAVE_ZLIB_H */
+#endif /* LIBXML_LZMA_ENABLED */
 
 #ifdef LIBXML_HTTP_ENABLED
     xmlRegisterInputCallbacks(xmlIOHTTPMatch, xmlIOHTTPOpen,
@@ -2683,7 +2683,7 @@
 #endif
 	}
 #endif
-#ifdef HAVE_LZMA_H
+#ifdef LIBXML_LZMA_ENABLED
 	if ((xmlInputCallbackTable[i].opencallback == xmlXzfileOpen) &&
 		(strcmp(URI, "-") != 0)) {
             ret->compressed = __libxml2_xzcompressed(context);
@@ -3350,7 +3350,7 @@
      * try to establish compressed status of input if not done already
      */
     if (in->compressed == -1) {
-#ifdef HAVE_LZMA_H
+#ifdef LIBXML_LZMA_ENABLED
 	if (in->readcallback == xmlXzfileRead)
             in->compressed = __libxml2_xzcompressed(in->context);
 #endif
diff --git a/xzlib.c b/xzlib.c
index 1fab546..782957f 100644
--- a/xzlib.c
+++ b/xzlib.c
@@ -8,7 +8,7 @@
  */
 #define IN_LIBXML
 #include "libxml.h"
-#ifdef HAVE_LZMA_H
+#ifdef LIBXML_LZMA_ENABLED
 
 #include <string.h>
 #ifdef HAVE_ERRNO_H
@@ -34,7 +34,9 @@
 #ifdef HAVE_ZLIB_H
 #include <zlib.h>
 #endif
+#ifdef HAVE_LZMA_H
 #include <lzma.h>
+#endif
 
 #include "xzlib.h"
 #include <libxml/xmlmemory.h>
@@ -799,4 +801,4 @@
     xmlFree(state);
     return ret ? ret : LZMA_OK;
 }
-#endif /* HAVE_LZMA_H */
+#endif /* LIBXML_LZMA_ENABLED */