Maptool not built / Maptool not running due to missing libnavit-core.so

[metalstrolch]

• Current cmake build fail to properly detect protobuf-c causing Maptool not to be built.

• Current cmake tries to build with shared libnavit-core.so. unfortunately nothing installes the built lib as it seems causing maptool / navit to fail.

PR #1305 fixes this issue,

[christf]

#1305 is merged. do we still need this issue?