configure: Fix checking for perl

Closes #1196
Fixes #1197
Warning cleanup

- ignoring const
- declarations after statements
- some C files didnt include own headers (risking them getting out of sync)

Closes #1064
ssl: Don't use global openssl context

Fixes #789
ssl: Use more secure options

This disables ssl 2/3
ssl: Validate hostnames

Closes #524
Fix possible crash in SASL Blowfish mech
Bump updater version to 2.10.2
Fix building against openssl 0.9.8

Closes #1221
Fix handling --cfgdir

Fixes #1225
 Fix compilation on Windows
Fix duplicate timestamps on selection

Fixes #1226
Fix copying timestamp with server-time and indent nicks off
configure: Add option to run clang static analysis
Add missing dependencies for glib's g_spawn on windows
Fix some obvious type warnings.
Store timer hook's timeout as milliseconds.
Always use 64-bit filesize and file offsets in DCC.

Based on LRN's commit for replacing stat with GFileInfo https://github.com/hexchat/hexchat/commit/32008bb

Fixes #382
Update travis notification format
Don't leak filename_fs on errors.
Removed some unnecessary null-checks for calls to g_free and g_strfreev