meson: Simpler meson options

Remove 'enable-' prefix from most options.
3 jobs for master in 8 minutes and 16 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #8608
ubuntu-16.04

00:08:04

passed #8609
ubuntu-17.10

00:08:16

passed #8610
ubuntu-18.04

00:08:08