Store character vectors in .mat files (-v6 or -v7) as UTF-16 (bug #58368). * ls-mat5.cc (read_mat5_binary_element): Convert UTF-16 and UTF-32 vectors to UTF-8. Take UTF-8 as is. Fall back to replacing non-ASCII characters with "?" for non-convertable strings or ND arrays. (maybe_convert_to_u16): Add function that converts a string vector to UTF-16. (save_mat5_element_length): Get correct length if string is converted. (save_mat5_binary_element): Convert character vectors to UTF-16 to be able to correctly load them in Matlab if they contain non-ASCII characters. * load-save.cc: Add tests for saving and loading different types of strings. * unistr-wrappers.h, unistr-wrappers.cc (octave_u16_to_u8_wrapper, octave_u32_to_u8_wrapper, octave_u8_to_u16_wrapper): New wrappers for gnulib functions. * bootstrap.conf: Add gnulib modules to list.

--- a/bootstrap.conf	Mon May 18 16:03:50 2020 +0200
+++ b/bootstrap.conf	Fri May 15 23:03:24 2020 +0200
@@ -117,9 +117,12 @@
   unictype/ctype-upper
   unictype/ctype-xdigit
   unistd
+  unistr/u16-to-u8
+  unistr/u32-to-u8
   unistr/u8-check
   unistr/u8-strmblen
   unistr/u8-strmbtouc
+  unistr/u8-to-u16
   unistr/u8-to-u32
   unlink
   unsetenv