Ugrade time functions to accept millisecond format string FFF (Bug #34586) * datestr.m: Add millisecond FFF format. Change numerical formats 21,22,29 to match Matlab. Remove unused persistent variables. Vectorize some for loops. Use strrep rather than regexp where possible for speed. * datevec.m: Add millisecond FFF format. Use strrep rather than regexp where possible for speed. * datenum.m: Update docstring. Use modern coding style. Only calculate second output argument if requested. Allow cellstr inputs.

--- a/NEWS
+++ b/NEWS
@@ -65,6 +65,12 @@
                Default options are "Qt Qbb Qc Qx" for 4D and higher
     voronoi  : No default arguments
 
+ ** Date/Time functions updated.
+    Millisecond support with FFF format string now supported.
+
+    datestr : Numerical formats 21, 22, 29 changed to match Matlab.
+              Now accepts cellstr inputs.
+
  ** Octave warning IDs updated
     "empty-list-elements" : removed
     "fortran-indexing"    : removed