more cleanups based on sparse reports, added "make sparse" Daniel

* Makefile.am globals.c parserInternals.c xmlreader.c xmlunicode.c
  xmlwriter.c: more cleanups based on sparse reports, added
  "make sparse"
Daniel
diff --git a/xmlwriter.c b/xmlwriter.c
index 6224222..6227398 100644
--- a/xmlwriter.c
+++ b/xmlwriter.c
@@ -739,7 +739,7 @@
         return -1;
     }
 
-    p->name = 0;
+    p->name = NULL;
     p->state = XML_TEXTWRITER_COMMENT;
 
     xmlListPushFront(writer->nodes, p);
@@ -1018,7 +1018,7 @@
     if ((writer == NULL) || (name == NULL) || (*name == '\0'))
         return -1;
 
-    buf = 0;
+    buf = NULL;
     if (prefix != 0) {
         buf = xmlStrdup(prefix);
         buf = xmlStrcat(buf, BAD_CAST ":");
@@ -1745,7 +1745,7 @@
     if ((writer == NULL) || (name == NULL) || (*name == '\0'))
         return -1;
 
-    buf = 0;
+    buf = NULL;
     if (prefix != 0) {
         buf = xmlStrdup(prefix);
         buf = xmlStrcat(buf, BAD_CAST ":");
@@ -2063,7 +2063,7 @@
     if ((writer == NULL) || (name == NULL) || (*name == '\0'))
         return -1;
 
-    buf = 0;
+    buf = NULL;
     if (prefix != NULL) {
         buf = xmlStrdup(prefix);
         buf = xmlStrcat(buf, BAD_CAST ":");
@@ -2078,7 +2078,7 @@
     sum += count;
 
     if (namespaceURI != NULL) {
-        buf = 0;
+        buf = NULL;
         buf = xmlStrdup(BAD_CAST "xmlns");
         if (prefix != NULL) {
             buf = xmlStrcat(buf, BAD_CAST ":");
@@ -2587,7 +2587,7 @@
         return -1;
     }
 
-    p->name = 0;
+    p->name = NULL;
     p->state = XML_TEXTWRITER_CDATA;
 
     xmlListPushFront(writer->nodes, p);