Enable the use of the viewport meta tag

SSIA. Add '--enable-viewport-meta' command line argument
by default.
Merge pull request #1753 from pozdnyakov/Viewport_meta

Enable the use of the viewport meta tag
Fix Mac build.

- Result of comparison against a string literal is unspecified (use strncmp instead).
- Explicit destructors.
- Invalid conversion NULL -> bool.
Merge pull request #1758 from darktears/mac-build

Fix Mac build.
Bump version to 6.34.110.0
Bump version to 6.34.111.0