[xml] typo corrections for FAQ

[Robert Funnell <funnell funsan biomed mcgill ca>]

To help improve an already excellent page, I'd like to suggest the
following very minor fixes to http://xmlsoft.org/FAQ.html :

As most UNIX libraries libxml follows the "standard"
->
As do most UNIX libraries, libxml follows the "standard"

won't impact other part of the content
->
won't impact other parts of the content

Libxml does not requires any other library
->
Libxml does not require any other library

libz : a highly portable and available widely compression library
->
libz : a highly portable and widely available compression library

There is however a few C++ wrappers
->
There are, however, a few C++ wrappers

or documents who have been built from scratch
->
or documents which have been built from scratch

- Robert