Fix 'transpose-regions' when LEAVE-MARKERS arg is non-nil

Fix 'transpose-regions' when LEAVE-MARKERS arg is non-nil

* src/insdel.c (adjust_markers_bytepos): New function.
* src/lisp.h (adjust_markers_bytepos): Add prototype.
* src/insdel.c (replace_range, replace_range_2):
* src/editfns.c (Ftranspose_regions): Call
adjust_markers_bytepos.  (Bug#5131)

* test/src/editfns-tests.el (transpose-test-reverse-word)
(transpose-test-get-byte-positions): New functions.
(transpose-ascii-regions-test)
(transpose-nonascii-regions-test-1)
(transpose-nonascii-regions-test-2): New tests.