Fix OpenSSL detection on distributions which modify the version number.
Merge pull request #407 from SaberUK/insp20+fix-openssl-detection

Fix OpenSSL detection on distributions which modify the version number.
Use GNU install on Solaris.
m_chanhistory Fix durations containing 'S' being rejected
m_ssl_gnutls Fix build with GnuTLS 1.x

Fixes #409 reported by @SaberUK
Use a better server name in m_httpd.
Use the preprocessor to detect whether hash_map is available.
Merge pull request #413 from SaberUK/insp20+httpd

[2.0] Use a better server name in m_httpd.
Merge pull request #414 from SaberUK/insp20+hashmap

[2.0] Use the preprocessor to detect whether hash_map is available.
Remove unused variables detected by Clang 4.2.
Merge pull request #416 from SaberUK/insp20+clang42-warnings

Remove unused variables detected by Clang 4.2.
Fix exactly <limits:maxchan> long channel names being truncated

Fixes #422 reported by @RawrDragon
cmd_invite Correct error message when the user has no privs to invite and no halfop prefix is available
cmd_invite Send invite announcements to halfops and higher when <security:announceinvites> is 'dynamic' regardless of the channel being +i or not

Clarify what the various options mean in the doc

Fixes #418 reported by @RawrDragon
Fix multiple escape bugs in m_httpd_stats.
m_ssl_gnutls Fix null pointer dereference in case gnutls_xxx_get_name() returns NULL