Bring up the sfnt-android font driver

Bring up the sfnt-android font driver

* configure.ac (ANDROID_CFLAGS): Add sfnt-related font objects
to ANDROID_OBJ when not building stubs.
* lisp/startup.el (android-fonts-enumerated): New variable.
(normal-top-level): Set it.  Also enumerate fonts as early as
possible upon startup.

* src/alloc.c (cleanup_vector): Only finalize Android font
entities.
(garbage_collect): Mark sfntfont.c.

* src/android.c (struct android_emacs_drawable): New field
`damage_rect'.
(android_init_emacs_drawable): Initialize
Lorg/gnu/emacs/EmacsDrawable;#damageRect(Landroid/graphics/rect;)V.
(android_create_gc): Initialize cached GC fields.
(android_free_gc): Free cached GC clip rectangles.
(android_change_gc): Cache fields as appropriate.
(android_set_clip_rectangles): Set cached clip rectangles for
easy access from C.
(android_get_gc_values): Use cached values.
(android_get_image): Remove obsolete comment.
(android_lock_bitmap, android_damage_window): New functions that
don't parallel anything on X.

* src/android.h: Update prototypes.

* src/androidfns.c (android_default_font_parameter): Set Droid
Sans Mono as the default monospace font.
(Fx_create_frame): Register the sfntfont driver.

* src/androidgui.h (struct android_gc): Add C side caches for
clip rectangles and the foreground and background colors.

* src/androidterm.h: Update prototypes.

* src/dispextern.h (struct gui_box): New struct.
(gui_union_rectangles): New function.

* src/emacs.c (android_emacs_init): Initialize Android font
stuff late.
* src/font.c (font_make_entity): Clear `is_android' field on
Android.
(font_make_entity_android): Set `is_android' field.
* src/font.h (struct font_entity): New field `is_android'.

* src/print.c (print_vectorlike): Don't print private data,
which could include Lisp_Misc.

* src/sfnt.c (sfnt_read_cmap_format_0, sfnt_read_cmap_format_2)
(sfnt_read_cmap_format_4, sfnt_read_cmap_format_6)
(sfnt_read_cmap_format_8, sfnt_read_cmap_format_12): Remove
buggy pragmas.
(sfnt_lookup_glyph_4_1): New function.
(sfnt_lookup_glyph_4): Handle malformed lookup tables found on
Android.
(sfnt_lookup_glyph): Fix overflow problems in glyph checks.
(sfnt_read_glyph): Handle empty glyphs.  This implements some
behavior which everyone else seems to as well, but I can't find
documented in the TrueType Reference Manual.
(sfnt_free_glyph): Export correctly.
(sfnt_transform_coordinates): Make faster.
(sfnt_lerp_half): Fix lerping in some cases.
(sfnt_decompose_glyph): Handle empty glyphs correctly.  Close
contours manually instead of waiting for the edge building
process to do that.  This lets curves be handled correctly.
(struct sfnt_build_glyph_outline_context): Move internal struct
back to sfnt.c.
(sfnt_build_append): Fix detection of initial entry.
(sfnt_curve_to_and_build_1): Fix De Casteljau implementation.
(sfnt_curve_to_and_build): Use fixed point arithmetic to scale
outlines.
(sfnt_build_glyph_outline): Clear reference counts.  Use fixed
point arithmetic.
(sfnt_prepare_raster): Align rasters to 4 bytes,
SFNT_POLY_ALIGNMENT.  Fix calculation of offx and offy.
(sfnt_step_edge_by): Step edge by previously computed step_x.
(sfnt_build_outline_edges): Adjust for already closed contours.
Ignore edges abandoned after grid fit.  Also precompute step_x
to avoid multiplication on each span rastered.
(sfnt_poly_edges): Improve alignment.
(sfnt_fill_span): Rewrite to avoid control flow in while loop.
(sfnt_poly_span): Remove unnecessary code.
(sfnt_raster_glyph_outline): Use raster stride instead of width.
(sfnt_test_edge, sfnt_test_raster, main): Improve debugging
code.

* src/sfnt.h (struct sfnt_glyph_outline): Add refcount field to
outline.
(struct sfnt_build_glyph_outline_context): Remove private
struct.
(struct sfnt_raster): Add refcount field to raster.
(struct sfnt_edge): Improve doc.  Add `source_x' field used when
built with TEST.
(SFNT_CEIL_FIXED): New macro.

* src/sfntfont-android.c (sfntfont_android_saturate32)
(sfntfont_android_scale32, sfntfont_android_mul8x2)
(sfntfont_android_blend, U255TO256)
(sfntfont_android_composite_bitmap, sfntfont_android_union_boxes)
(sfntfont_android_put_glyphs, sfntfont_android_get_cache): New
functions.
(android_sfntfont_driver): New font driver.
(Fandroid_enumerate_fonts): New function.
(syms_of_sfntfont_android_for_pdumper, init_sfntfont_android)
(syms_of_sfntfont_android): Initialize default fonts, special
family mapping and font driver.
* src/sfntfont.c (struct sfnt_font_desc): New fields
`char_cache', `cmap_invalid' and `subtable'.
(sfnt_setup_coding_system): Improve commentary.  Add default
branch.  Fix return value.
(sfnt_safe_encode_coding_object_1)
(sfnt_safe_encode_coding_object_2):
(sfnt_safe_encode_coding_object): Use decode_coding_object
instead of encode_coding_object.
(sfnt_decode_font_string): Adjust for rename.
(sfnt_decode_foundry_name): New function.
(sfnt_weight_descriptions, sfnt_slant_descriptions)
(sfnt_width_descriptions): Fix definitions.
(sfnt_parse_style): Make function work.
(sfnt_enum_font): Initialize designer, char-cache and subtable
platform ID.
(sfntfont_charset_for_name, mark_sfntfont)
(sfntfont_charset_for_cmap): New functions.
(syms_of_sfntfont): New variable `sfnt-default-family-alist'.

* src/sfntfont.h (_SFNTFONT_H_): Update prototypes.

* src/xdisp.c (gui_union_rectangles): New function.