interpreterbase: warn on redundant Meson version checks

[bgilbert]

We might encounter a Meson version check that always evaluates to true or to false:

project('t', 'c', meson_version: '>=0.60.0')
if meson.version().version_compare('>=0.55.0')
  v = 1
endif
if meson.version().version_compare('<0.60.0')
  v = 2
endif

Print warnings in such cases.

Only the innermost version dependency is available to us, so we don't catch cases like:

project('t', 'c', meson_version: '>=0.50')
if meson.version().version_compare('<0.60')
  v = 1
  if meson.version().version_compare('>=0.40')
    v = 2
  endif
endif

but such constructs aren't typical.