'random negative ids', until a better solution is found with upstream.
Fixes the 'oh i can't upload those new nodes to the server because they
have positive ids' annoying bug (that appeared since switching to gcc4 ?)
While here, switch to newer REVISION/LIB_DEPENDS.
Merkaartor is an openstreetmap mapping program written in C++/QT4. It
focuses on providing a visually pleasing but performant editing environment
for free geographical data.