Fix: compare against zero when invoking memcmp()
Merge pull request #259 from matthiasbeyer/hotfix-config_cmp

Hotfix: memcmp() call in config_cmp()
Add implementation for r_set_equal()
Added ll_equal() implementation
Started implementation for avl_equal()
Started implementation for ht_equal()
Added missing entries in CMakeLists file
Removed unneeded variable
Removed unneeded avl_equal function
Added implementation for ht_equal
Implemented avl_is_subset
Implemented ll_is_subset
Added source files to CMakeLists.txt
Fixed pointer type
Added missing file to CMakeLists
Added declaration of ll_is_subset
Fixed types
Added ll_is_subset tests
Fixed return values
Added subset tests