general: remove inline qualifiers and move in-header functions to objects

* (general) Move functions in headers into files, to be compiled into
  shared object files. Remove inline qualifier from functions. Let the
  compiler do the work.
diff --git a/zebra/interface.c b/zebra/interface.c
index 03e7ff7..933d642 100644
--- a/zebra/interface.c
+++ b/zebra/interface.c
@@ -216,7 +216,7 @@
  * interface will affect only the primary interface/address on Solaris.
  ************************End Solaris flags hacks ***********************
  */
-static inline void
+static void
 if_flags_mangle (struct interface *ifp, uint64_t *newflags)
 {
 #ifdef SUNOS_5