Merge pull request #1540 in SNORT/snort3 from ~RUCOMBS/snort3:fixups to master

Merge pull request #1540 in SNORT/snort3 from ~RUCOMBS/snort3:fixups to master

Squashed commit of the following:

commit 9dfe7aef3ff54dac76c31b0d37d5ee73620a6bd8
Author: russ <rucombs@cisco.com>
Date:   Sun Mar 10 18:30:23 2019 -0400

    memory: beware the perf_monitor, for she stealeth your numbers

commit 7f761152dbe6372064cc82b0281e5b3f0b1f7a33
Author: russ <rucombs@cisco.com>
Date:   Sun Mar 10 18:29:50 2019 -0400

    http_inspect: patch around buffer ownership confusion

commit 477697e8a464eaee0749780d283c2d0057561341
Author: russ <rucombs@cisco.com>
Date:   Sun Mar 10 18:29:19 2019 -0400

    build: fix constness warnings

commit 95a5d10e1455fda40b6f297946d648b935a1d20a
Author: russ <rucombs@cisco.com>
Date:   Sun Mar 10 18:28:52 2019 -0400

    build: fix always true warning