travis: Build with static analysis
Fix use after free
checksum: Use glib for io/checksum and misc fixes

- Fixes support for large files.
- Fixes filenames not being passed in the filename encoding.
- Drops openssl dependency.
- Code cleanup.
- Fix 'unknown command' warning.
configure: Improve various build flags

- Store openssl flags in own vars
- Share some common flags for plugins
- Fix building plugins on win32
- Store all glib flags in one var
- Don't link against every lib for each plugin
- Don't hardcode ldflags for sysinfo
Update .gitignore
Add patch from cygwin
Remove unused header
Fixed some more signed-unsigned-comparison warnings.