meson: Try building with -Wshorten-64-to-32

This adds a bunch more warnings, some similar to the ones produced
by MSVC by default.

meson.build

@@ -182,6 +182,7 @@ optional_arguments = [
   '-Wno-missing-field-initializers',
   '-Wno-unused-parameter',
   '-Werror=missing-prototypes',
+  '-Wshorten-64-to-32',
 ]
 if cc.get_id() == 'msvc'
     optional_arguments += [