Removed BSD license in favor LGPLv2.1
Added license header to all files
Removed note about how to apply the license
Inserted real empty lines where some not-printable character was
 Fixed README.md note on license
Merge pull request #45 from matthiasbeyer/change-license_to_lgplv2

Removed BSD license in favor of LGPLv2.1
Add libreset global include dir to local includes
Fix typedef
Fix includes in avl.c
Restructure avl.c
Add avl.c to sources of libreset.
Merge pull request #72 from neithernut/fix-avl-implementation_and_build

Fix avl implementation and build
Added implementation for avl_add() with helper
Added implementation for helper: new_avl_el()
Added implementation for helper: insert_element_into_tree()
Added implementation for helper: element_with_hash()
Added implementation for helper: inserting an element into the tree
Moved documentation for add()
Moved documentation for new_avl_el()
Moved documentation for insert_element_into_tree()