[xml] some compiler warnings

["Oliver Stöneberg" <oliverst online de>]

I just compiled the libxml2-2.6.10 release on a MinGW enviroment with 
mingw-runtime 3.3, win32api 2.5 and the candidate of the GCC 3.4.0 
compiler. I got following warnings. A few are just cosmetic, but I 
don't know, ifother might be more serious:

./include/libxml/parserInternals.h:250: warning: array 
'xmlStringText' assumed to have one element
./include/libxml/parserInternals.h:251: warning: array 
'xmlStringTextNoenc' assumed to have one element
./include/libxml/parserInternals.h:252: warning: array 
'xmlStringComment' assumed to have one element

uri.c: In function `xmlCanonicPath':
uri.c:1995: warning: unused variable `i'

trionan.c:217: warning: 'trio_is_negative' defined but not used

nanohttp.c:78:1: warning: "_WINSOCKAPI_" redefined
In file included from libxml.h:24,
                 from nanohttp.c:19:
config.h:276:1: warning: this is the location of the previous 
definition

catalog.c: In function `xmlCatalogGetSystem':
catalog.c:3536: warning: function returns address of local variable
catalog.c: In function `xmlCatalogGetPublic':
catalog.c:3580: warning: function returns address of local variable

c14n.c: In function `xmlC14NIsNodeInNodeset':
c14n.c:191: warning: dereferencing type-punned pointer will break 
strict-aliasing rules

I also couldn't link the xmllint.exe. I got the following errors:

xmllint.o(.text+0x114): In function `myStrdupFunc':
c:/libxml2-2.6.10/xmllint.c:231: undefined reference to 
`_imp__xmlFree'
xmllint.o(.text+0x24b): In function `xmlHTMLEncodeSend':
c:/libxml2-2.6.10/xmllint.c:383: undefined reference to 
`_imp__xmlFree

I know, that I ran into that problem in the past, but I can't 
remember how I fixed it. Been a few months since then :(