[gobject-introspection] (40 commits) ...meson: Rebase on top of latest master and bump version

[Emmanuele Bassi <ebassi src gnome org>]

Summary of changes:

  69fe98b... Initial work on meson port (*)
  142eeea... Windows: compile with /DYY_NO_UNISTD_H (*)
  083e6af... Declaration to export functions in girepository.dll/.lib, f (*)
  f206861... Fix dependency on giscanner's python module (*)
  a7c4e3d... Build docs (*)
  0a96d6c... Allow setting custom cairo-gobject libname (*)
  7a42b2a... meson: Set default values for some options (*)
  f1464c1... meson: Set EXEEXT for pkg-config files (*)
  47a07da... meson: Use ${prefix} in pkg-config files (*)
  a9471d4... meson: Set glib version from the project version (*)
  c2b2a76... meson: Add fallbacks for all dependencies (*)
  5d15d65... meson: Use glib_dep and configinc for girepository (*)
  8e8523a... meson: Fix configuration when libffi is a subproject (*)
  aae69e7... meson: Rewrite glib gir generation (*)
  3a7d3ee... giscanner: Remove custom collections implementation (*)
  e84c9e7... g-ir-scanner: Don't require SRCDIR and BUILDDIR env vars (*)
  31cac37... meson: Try to use win_flex and win_bison if available (*)
  fd28060... meson: Use giounix_dep from glib instead of libgio_dep (*)
  cde3376... meson: Explicitly use python3 for running g-ir-scanner (*)
  4563e35... meson: Fix include dir for gir and typelib gen (*)
  307505c... meson: typelib build depends on GObject-2.0.Gir (*)
  aa3d092... meson: Fix build without pkg-config or any system libs (*)
  17323d2... giscanner: Fix options in the preprocessor group (*)
  088d067... meson: Have a single place to set the subproject directory (*)
  c0be7bc... meson: Update symbol visibility rules (*)
  5d68eb7... meson: Use symbol visibility for giscanner module (*)
  e1f45a0... meson: Bump up the Meson version (*)
  3adde9e... meson: Fix including of config.h (*)
  7c98ef9... meson: Remove gir_build hack option (*)
  97904f7... meson: Handle spaces in the full python path (*)
  b506869... Revert "meson: Handle spaces in the full python path" (*)
  52a5c7e... The third parameter of assertion_message is an integer. (*)
  1a0aa37... meson: Don't look for gio-unix-2.0 on Windows (*)
  5c46869... giscanner: Fix GtkDocAnnotations implementation (*)
  2034e30... meson: Prefer source annotations for gir generation (*)
  b9693d3... giscanner: Fix minor python3 compatibility issue (*)
  daf5d25... meson: Sort globbed files before printing (*)
  d010472... giscanner: Maintain python2 compat in annotationparser (*)
  9aabc17... meson: add ffi_libdir to glib_libpaths and glib_command (*)
  10a369f... meson: Rebase on top of latest master and bump version (*)

(*) This commit already existed in another branch; no separate mail sent