Merge branch 'release-3.8.13' into 'master'

Release 3.8.13

Closes #1820, #1817, #1823, #1822, #1819, #1854, #1808, #1815, #1801, #1812, #1840, #1814, #1766, #1809, #1825, #1849, #1802, #1824, #1223, #1803, #1852, #1864, #1850, #1811, #1848, #1839, #1816, and #1838

See merge request gnutls/gnutls!2102