[xml] xmlIO enhancements?

[Joel Reed <joelwreed comcast net>]

I'm reviewing xmlFileOpen_real and xmlGzfileOpen_real in xmlIO.c and have
two quick questions/possible improvements (i'll fire off a patch if no
dissenters).

1) xmlFileOpen_real does a

  if (!xmlCheckFilename(path)) return(NULL);

before the fopen(path, "r") call. This quick-out prevents library users
from ever seeing a message in their structure error handler like
"No such file or directory." By deleting this check, we can let fopen call
fail and set errno, then let normal libxml error handling bubble the
error back up to library users. Any reason why not to do this?

2) Any reason not to enhance the last line of __xmlIOErr:

  __xmlSimpleError(domain, code, NULL, IOerr[idx], extra);

to say

  __xmlSimpleError(domain, code, strerror(errno), IOerr[idx], extra);

if this change passes all tests i'll submit a patch unless someone
thinks it a bad idea.

3) xmlGzfileOpen_real does not have anything like: 

    if (fd == NULL) xmlIOErr(0, path);

after the gzopen(path, "rb") call, unlike xmlFileOpen_real. this
minor inconsistency could be addressed easily enough. Any reason not to?

jr

p.s. have a good vacation dv!