Minor bug-fixes discovered by static analysis.

[Oliver McFadden]

Hi,

This is the same as the pull request, but in easier to review patch format. I
have added Matt Turner's Reviewed-by lines to the patches he checked as OK.

[PATCH 1/5] exa: exaFinishAccess: Overrun of static array "pExaScr->access" of size 6 at position 6 with index variable "i"
[PATCH 2/5] fb: fbFinishScreenInit: leaked_storage: Variable "(visuals|depths)" goes out of scope
[PATCH 3/5] parser: xf86readConfigFile: unreachable: This code cannot be reached: "free(val.str);"
[PATCH 4/5] common: xf86Configure: alloc_strlen: Allocated memory does not have space for the terminating NUL of the string
[PATCH 5/5] Xext: IdleTimeBlockHandler: unsigned_compare: Comparing unsigned less than zero is never true. "timeout < 0UL"

I think the last one (IdleTimeBlockHandler: unsigned_compare) might not be
enough, but then that's the whole point of the review process.

P.S. I am on vacation currently so please accept my apologies if my replies are
delayed.

Regards,
-- Oliver.