added Tst/short/Short/symodstd.*

it is rest of commit 8979f91:

modstd.lib: Example in modpStd has been changed.
symodstd.lib: Library for computing Groebner basis of symmetric ideals.

Conflicts:
	Singular/LIB/modstd.lib
	Singular/LIB/symodstd.lib
Merge pull request #270 from mohamed-barakat/spielwiese

added Tst/short/Short/symodstd.*
added symodstd.tst to Tst/Short.lst
updated docu + bugfixes
Merge pull request #272 from mohamed-barakat/spielwiese

added symodstd.tst to Tst/Short.lst