* Meson: remove space before colon
Since key-value pairs in Python are usually delimited as
colon+space instead of space+colon+space.
* Meson: disable modules by default when building static libraries
Corresponds to autotools. See: #2323.
* Meson: make modules a feature option
Corresponds to autotools, where modules are built
automatically if enabled and supported.
* Meson: specify minimum required GLib version
* Meson: fix indentation
* Remove unused function checks
* Simplify GLib configure checks
* Meson: ensure modules doesn't include enumtypes sources
Since that would cause duplicate symbols.
(`soname_header` can also be safely removed here,
since that is already included in `libvips_headers_dep`)
