Cleanup in ac-tile MPM

Remove return from void functions.
Add some commments
Remove inline on functions where it doesn't make sense.
Rewrote if statement to be more clear.
When assigning Pattern IDs pids, check Case flags

This fixes bug 1110. When assigning PIDs, use the NO_CASE flag when comparing
for duplicates. The state of the flag must be the same, but also use the same
type of comparisons when checking for duplicates.

Previously, "foo":CS would match with "foo":CI when it should not.
and "foo":CI would not match "FoO":CI when it should. Both of those
cases are fixed with this change.

This then allows simplifying the use of pid in MPMs because now if they
pids match, then so do the flags, so checking the flags is not required.
Remove case_state usage

The case_state in MPMs was just to track when a pid could have no-case and
case-sensitive matches for the same PID. Now that can't happen after fixing
bug 1110, so remove the code and storage for case_state.
Store case-insensitive patterns as lowercase.

This is required because SCMemcmpLowercase() expects it first argument
to be already lowercase for the comparison. This is done by using
memcpy_tolower() for NO_CASE patterns.

This addresses code review comments from Victor.