Minor tweaks

Make functions and variables static whenever possible.

style(9) says:
"Function prototypes for private functions (i.e., functions not used
elsewhere) go at the top of the first source module. In userland,
functions local to one source module should be declared 'static'".

The benefits of doing so include:
* clean up of the eigrpd global namespace;
* improved readability;
* more hints to the compiler/linker to generate more efficient code.

Additional changes:
* Declare all extern variables in header files;
* Clean up the indentation of all function prototypes and global
variables.

ok claudio@ benno@

Remove superfluous includes and follow style(9).

ok claudio@ benno@

Fix warnings and add safeguards to protect against corrupted data.

Welcome eigrpd

The eigrpd daemon will support the Enhanced Interior Gateway Routing Protocol.

Built using the imsg/three process framework and heavily based on ospfd(8), ospf6d(8) and ldpd(8).

The current status of eigrpd(8) is as follows:
* Almost full compliance with the specification: DUAL FSM, RTP, CR mode, SIA, etc
* Support for both IPv4 and IPv6
* Support for multiple instances (different ASes/AFs) within the same process
* Support for rdomains (one process per rdomain)
* RIB/FIB synchronization
* Basic redistribution support

Not implemented features (yet):
* Configuration reload support (partially implemented)
* Route summarization
* Advanced route redistribution/filtering
* Carp integration
* Authentication (draft is missing information)
* Stub (not released by Cisco)

Not yet connected to the builds.

ok deraadt@ claudio@