More warning fixes

[Cyril Brulebois]

Hi,

some more patches to fix warnings:
 - [PATCH 1/3] Fix missing <string.h> include.
   I might be missing but that should be pretty straightforward to
   ACK/NACK.

 - [PATCH 2/3] Replace LookupIDByType() with dixLookupResourceByType(), take 1.
   Used coccinelle for that one. Indentation was kind of ugly already, I
   tried not to insert more ugliness, but might fail.

 - [PATCH 3/3] Replace LookupIDByType() with dixLookupResourceByType(), take 2.
   The remaining bits of LookupIDByType.

More patches for SecurityLookupIDBy{Type,Class} removal might come
later.

Mraw,
KiBi.