[librsvg] (8 commits) ...Merge branch 'c_api_crate'

[Federico Mena Quintero <federico src gnome org>]

Summary of changes:

  577dcfd... Handle::get_bbox_for_element() - Factor out duplicated code
  c8540b9... handle.rs: Extract function to create a unit rectangle
  c2811e0... c_api.rs: Check the incoming cairo context here to emit a g
  3e11049... c_api.rs: Warn when passing external references here, not i
  d8495a0... Move rsvg_g_warning() and rsvg_g_critical() to c_api.rs
  7821989... Move C API glue to a librsvg_c_api crate
  38fe68c... Remove the c-library feature for the librsvg_c_api crate
  683d92c... Merge branch 'c_api_crate'