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
Merge pull request #72 from neithernut/fix-avl-implementation_and_build

Fix avl implementation and build
Make height unsigned
Make documentation of member ll apply to 80c rule

The line was too long because of the extra intend added when changing
the type of the member "height".
Modify getter return type
Store number of nodes of a subtree in the root node
Add inlined getter for the node count of a subtree