Merge branch 'PHP-7.3' into PHP-7.4

* PHP-7.3:
  Fixed bug #78910
  Fix #78878: Buffer underflow in bc_shift_addsub
  Fix test
  Fix #78862: link() silently truncates after a null byte on Windows
  Fix #78863: DirectoryIterator class silently truncates after a null byte
  Fix #78943: mail() may release string with refcount==1 twice

diff --cc ext/bcmath/libbcmath/src/str2num.c
Simple merge

diff --cc ext/exif/exif.c
Simple merge

diff --cc ext/spl/spl_directory.c
Simple merge

diff --cc win32/sendmail.c
Simple merge