Fix library categories

fix: "System and Control theory" -> "System and Control Theory"
fix: 'Commutative algebra' -> 'Commutative Algebra'
chg: also corresponding changes to emacs files (although they should better be generated in build time)
library that computes hdepth_1 of a module M
Updated hdepth.lib, added tests for the functions
updated test hdepth.tst
chg: hdepth.stat and .res
fix: added hdepth.lib in slingular-libs
sync grammar.y
fix: tr. 599 (assign expr_list to def should yield an error)
chg: tests changed (fix tr.599, asssign expr_list to def)
test for tr.599
Merge pull request #377 from adipopescu/hdepth

library that computes hdepth_1 of a module M
Bugfix 541 mathematically correct, but not final solution
added update: bug fix for bug #541 second example
Added Bug 541 as tests
Added Tests
add: Warn message for interred