pango: Update to version 1.50.3

pango: Update to version 1.50.3

- Update from 1.50.0 to 1.50.3
- Update of rootfile
- Changelog
   Overview of changes in 1.50.3, 21-12-2021
     * pango-view: Add --serialize-to option for easy bug reporting
     * Revert a transformation change that broke metrics for vertical text
     * Handle fonts without space glyph (such as icon fonts) better
     * Fix some corner cases of line width accounting
     * Fix line height with emulated Small Caps
   Overview of changes in 1.50.2, 16-12-2021
     * Fix a problem with font fallback for Arabic
     * Fix handling of fonts without a space glyph
     * Various documentation improvements
     * Fix build issues
   Overview of changes in 1.50.1, 10-12-2021
     * Fix a crash in tab handling
     * Fix tab positioning without line wrapping
     * Fix an assertion failure found by fuzzing
     * Make underlines work again for broken fonts

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>