Wrong feature name

Use crates in master, update versions

Revert "Use crates in master, update versions"

Add quartz functions

These functions had parameters incorrectly marked as ptr-to-mutable
while the C declarations have these parameters as ptr-to-immutable.

cairo_scaled_font_text_extents takes a *const c_char not a *mut c_char.
cairo_scaled_font_glyph_extents takes a *const Glyph not a *mut Glyph.
cairo_scaled_font_text_to_glyphs takes *const c_char not *mut c_char.

See https://cairographics.org/manual/cairo-cairo-scaled-font-t.html

This adds the following new functions:

ScaledFont::extents
ScaledFont::text_extents
ScaledFont::glyph_extents
ScaledFont::text_to_glyphs

This function has a large unsafe block due to
cairo_scaled_font_text_to_glyphs returning two pointers that are
allocated using opaque methods, i.e. not under our control, and so must
be copied into Vec<>'s.

The other option would have been to return a special container type for
[Glyph] and [TextCluster] that called the relevant
cairo_{glyph,text_cluster}_free function upon drop. Less copying but
greater complexity and poor ergonomics.

ScaledFont::get_font_face
ScaledFont::get_font_options

I opted for an explicit allocation and return of a FontOptions structure
(wrapped opaque pointer) instead of allowing a caller to pass in an &mut
FontOptions as I felt that wasn't idiomatic Rust code.

ScaledFont::get_font_matrix
ScaledFont::get_ctm
ScaledFont::get_scale_matrix

glyphs is *const and not *mut.

See
https://www.cairographics.org/manual/cairo-Paths.html#cairo-glyph-path

Scaled fonts

impl *GlibPtr* for font types, make raw pointer fields private

Because `glib_wrapper!` can only be applied once per module.

Proper glib bindings for font types

Fix parameters for ImageSurface::create_from_png and write_to_png

cairo-sys: fix enum types

The cairo bindings used the glib::translate traits to handle internal
reference counting discipline. However, these are not actually
required, and should be possible to use cairo without a dependency on
glib. This patch makes the dependency optional, and changes the
implementation to not use the glib traits internally.

Make glib dependency optional