Improve text display on Android port

Improve text display on Android port

* src/sfnt.c (sfnt_build_glyph_outline): Clear
build_outline_context.
(sfnt_poly_coverage): Extend coverage map.
(sfnt_prepare_raster): Always floor coordinates, since the
increase in coverage makes this hack unnecessary.
(sfnt_build_outline_edges): Likewise.
(sfnt_compare_edges): Remove function.
(sfnt_edge_sort): New function.  Since edges are already
partially sorted, and there are not many, insertion sort
suffices.
(sfnt_poly_edges): Use sfnt_edge_sort.
(sfnt_fill_span): Stop rounding x0 and x1 to the grid, and make
coverage computation static.
(sfnt_lookup_glyph_metrics): Fix return code for unscaled
metrics.
(sfnt_scale_metrics): New function.
(SFNT_ENABLE_HINTING): Remove define.
(struct sfnt_cvt_table, struct sfnt_fpgm_table)
(struct sfnt_prep_table): Move to sfnt.h.
(sfnt_read_cvt_table):
(sfnt_read_fpgm_table, sfnt_read_prep_table): Make TEST_STATIC.
(struct sfnt_unit_vector, struct sfnt_interpreter_definition)
(struct sfnt_interpreter_zone, struct sfnt_graphics_state):
(struct sfnt_interpreter): Move to sfnt.h.
(sfnt_make_interpreter): Make TEST_STATIC.
(POP, PUSH, DELTAP1, DELTAP2, DELTAP3): When TEST, define to
regular push and pop.
(sfnt_deltac):
(sfnt_deltap): Fix order of arguments.
(IUP_SINGLE_PAIR): Fix interpolation loop wraparound.
(sfnt_interpret_font_program):
(sfnt_interpret_control_value_program): Make TEST_STATIC.
(struct sfnt_instructed_outline): Move to sfnt.h.
(sfnt_build_instructed_outline): Make TEST_STATIC.
(sfnt_interpret_simple_glyph):
(sfnt_x_raster):
(sfnt_test_raster):
(all_tests):
(sfnt_verbose):
(main): Improve test code.

* src/sfnt.h (SFNT_ENABLE_HINTING, struct sfnt_cvt_table)
(struct sfnt_fpgm_table, struct sfnt_prep_table)
(struct sfnt_unit_vector, struct sfnt_interpreter_definition)
(struct sfnt_interpreter_zone, struct sfnt_graphics_state)
(struct sfnt_interpreter, struct sfnt_instructed_outline)
(PROTOTYPE): New definitions.
* src/sfntfont-android.c (sfntfont_android_put_glyphs): Make
coordinate generation more straightforward.
* src/sfntfont.c (sfntfont_get_glyph_outline): New arguments
INTERPRETER and METRICS.
(struct sfnt_font_info): New tables.
(sfntfont_setup_interpreter): New function.
(sfntfont_open): Avoid memory leak.  Set up interpreter.
(sfntfont_measure_instructed_pcm): New function.
(sfntfont_measure_pcm): Delegate to measure_instructed_pcm where
appropriate.
(sfntfont_close): Free new tables.
(sfntfont_draw): Scale metrics properly.