Define seq_concat variants in the same order as in m3expl

The last commit exchanged the order in which seq_concat:ccc
and seq_gconcat:NNN were defined.  Rather than changing two
test files, I've opted for swapping in the source.


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@4422 de43f980-851b-0410-b2f7-c40aca1f87e0
Change \__prop_split:NnTF, less prop auxiliaries.

The T and F branches of \__prop_split:NnTF now receive
the various pieces of the prop as #1, #2, #3, rather than
as three brace groups.  This turns out to require less
auxiliaries, but more importantly, arguments are read one
time less, which leads to speed ups for large props (but
a slight slow down for small props).


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@4423 de43f980-851b-0410-b2f7-c40aca1f87e0