minirpcgen: Protect against multiple definition of free functions
minirpcgen: Protect against multiple definition of free functions

- Make generated free functions static inlines and move them to *_minirpc.h,
protected by ifdefs that prevent redefinitions.  This allows multiple
protocols which use common data structures to coexist in the same
application.

cmusatyalab/minirpc,cmusatyalab/minirpc