libalias: Restructure

Clean up the database handling in order to switch to more efficient
data structures. The development of this patch was artificially split
in to many small steps to ease reviewing.

• Common search terms
• Separate fully qualified search
• Separate table for partial links
• Cleanup _FindLinkIn
• Factor out the outgoing search function
• Factor out a common idiom to return found links
• Reorder incoming links by grouping of common search terms
• Remove LSNAT from outgoing search
• Group internal structure semantically
• Separate table for PPTP
• Use AliasRange instead of PORT_BASE
• Remove temporary state deleteAllLinks from global struct
• Avoid uninitialized expiration

Discussed with: Dimitry Luhtionov
Differential Revision: https://reviews.freebsd.org/D30568
Differential Revision: https://reviews.freebsd.org/D30569
Differential Revision: https://reviews.freebsd.org/D30570
Differential Revision: https://reviews.freebsd.org/D30571
Differential Revision: https://reviews.freebsd.org/D30572
Differential Revision: https://reviews.freebsd.org/D30573
Differential Revision: https://reviews.freebsd.org/D30574
Differential Revision: https://reviews.freebsd.org/D30575
Differential Revision: https://reviews.freebsd.org/D30580
Differential Revision: https://reviews.freebsd.org/D30581
Differential Revision: https://reviews.freebsd.org/D30604
Differential Revision: https://reviews.freebsd.org/D30582

(cherry picked from commit d41044ddfdbc2a026570cae11d5fc2e18f5e4b92)
(cherry picked from commit 32f9c2ceb3ec8266e48ec0f6d1556fd98ef12db6)
(cherry picked from commit cac129e6030095c33e95c5ce1cdcb9c5c21efce9)
(cherry picked from commit 19dcc4f2250b3850991366e3058ca8a64b2f135d)
(cherry picked from commit d5419034381d0e8e8c99f0f678118b197144bfff)
(cherry picked from commit d4ab07d2aeb13b1aae9ad5d73e5fe77131f2350c)
(cherry picked from commit 492d3b7109b45ff30fd199b7eeed797447746e42)
(cherry picked from commit 7b44ff4c52ce9e7a89e772566a249e5481fe0ac4)
(cherry picked from commit 1178dda53d10b096e0b99e356d15b7c24390e099)
(cherry picked from commit 9efcad61d8309ecad3c15392b277fd329a1e45e4)
(cherry picked from commit fe83900f9fa931e3d0942ec9c0709896b887c3d7)
(cherry picked from commit d989935b5bcd880353f0de89eda958c45e7e3342)
(cherry picked from commit b50a4dce185481bebf8096c27588ae04a4a2fd7c)
(cherry picked from commit f28455344483310cfd1aa5c0bdd4d014810c0e32)