[libxml2] fix memory leak xml header encoding field with XML_PARSE_IGNORE_ENC

[Daniel Veillard <veillard src gnome org>]

commit 500c54ef326b62b8126e2d98d3a50f1a30dc5292
Author: Bart De Schuymer <deschuyb b-virtual org>
Date:   Thu Oct 16 12:17:20 2014 +0800

    fix memory leak xml header encoding field with XML_PARSE_IGNORE_ENC
    
    When the xml parser encounters an xml encoding in an xml header while
    configured with option XML_PARSE_IGNORE_ENC, it fails to free memory
    allocated for storing the encoding.
    The patch below fixes this.
    How to reproduce:
    1. Change doc/examples/parse4.c to add xmlCtxtUseOptions(ctxt,
    XML_PARSE_IGNORE_ENC); after the call to xmlCreatePushParserCtxt.
    2. Rebuild
    3. run the following command from the top libxml2 directory:
    LD_LIBRARY_PATH=.libs/ valgrind --leak-check=full
    ./doc/examples/.libs/parse4 ./test.xml , where test.xml contains
    following
    input:
    <?xml version="1.0" encoding="UTF-81" ?><hi/>
    valgrind will report:
    ==1964== 10 bytes in 1 blocks are definitely lost in loss record 1 of 1
    ==1964==    at 0x4C272DB: malloc (in
    /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
    ==1964==    by 0x4E88497: xmlParseEncName (parser.c:10224)
    ==1964==    by 0x4E888FE: xmlParseEncodingDecl (parser.c:10295)
    ==1964==    by 0x4E89630: xmlParseXMLDecl (parser.c:10534)
    ==1964==    by 0x4E8B737: xmlParseTryOrFinish (parser.c:11293)
    ==1964==    by 0x4E8E775: xmlParseChunk (parser.c:12283)
    
    Signed-off-by: Bart De Schuymer <bart at amplidata com>

 parser.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/parser.c b/parser.c
index b9a37ab..f51e8d2 100644
--- a/parser.c
+++ b/parser.c
@@ -10378,8 +10378,10 @@ xmlParseEncodingDecl(xmlParserCtxtPtr ctxt) {
         /*
          * Non standard parsing, allowing the user to ignore encoding
          */
-        if (ctxt->options & XML_PARSE_IGNORE_ENC)
-            return(encoding);
+        if (ctxt->options & XML_PARSE_IGNORE_ENC) {
+           xmlFree((xmlChar *) encoding);
+            return(NULL);
+       }
 
        /*
         * UTF-16 encoding stwich has already taken place at this stage,