dead stores in msxml3

[Piotr Caban]

Hi Ricardo,
There are few things that needs to be changed in 'dlls/msxml3: check dead 
stores (llvm/clang)' patch. Some of the 'hr != S_OK' should not be replaced 
with 'FAILED(hr)'. Sometimes the parser should stop if user returns anything 
except S_OK.

Changes in following functions are incorrect:
 - libxmlStartDocument
 - libxmlEndDocument
 - libxmlStartElementNS
 - libxmlEndElementNS
 - libxmlCharacters

> i'm tracking some dead stores with Clang and there are some in
> dlls/msxml3/saxreader.c i'm hoping you can tell me if the stores are to be
> removed for performance or if they should be checked in each iteration for
> correctness: file dlls/msxml3/saxreader.c
> lines:
> 1163
> 1166
It should be checked in every iteration, if something goes wrong 
format_error_message_from_id should be called (it stops the parser and sets 
error code).  The parser should stop if user returns anything except S_OK.
> 1213
> 1216
The same here.

Regards,
Piotr Caban