Moved indent file to after. Changed parser.

The indentation file was moved to the after directory: the reason is
that otherwise the system-wide tex indentation code is run *afer*
TeX-9's, rendering the latter useless (indentation-wise).

Further, the open and end patterns where changed in order to accomodate
optional sectioning arguments:

openingpat:
original: '\\\(begin\|section\*\=\|paragraph\*\=\){\(.*\)}'
new     : '\\\(begin\|section\*\=\|paragraph\*\=\)\(\[.\+\]\)\={\(.*\)}'

endpat:
original: '\\\(end\|section\*\=\|paragraph\*\=\){\(.*\)}'
new     : '\\\(end\|section\*\=\|paragraph\*\=\)\(\[.\+\]\)\={\(.*\)}'