* set some -Ds depending on the release type
libvips uses g_assert() quite a bit to check things like pointer bounds,
and this can have a large performance impact.
This PR turns off g_assert() (plus some other things) in release mode,
and enables leak checking (and some other things) in debug mode.
I'm not sure if this is the best way to implement this kind of thing.
Does meson have a more offical path for this?
* incorporate comments
* link asserts and cast checks to optimization level
* 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`)
