historically, glibc provided all the ugly rpc support (while not nearly as 
relevant today, it still is used by way of nfs support).  the glibc 
maintainers have opted to stop supporting this.  at first they declined to 
accept new features, but now they've started removing support for new code to 
build against it.

libtirpc started off to support the new features (namely ipv6 support), but 
has now taken on a new roll of supporting all the rpc code.

so if you have a build bug due to glibc-2.14 due to missing rpc/ or rpcsvc/ 
header, you're going to have to convert over to libtirpc.

something like:
	inherit toolchain-funcs
	...
	append-cppflags $($(tc-getPKG_CONFIG) libtirpc --cflags)
	export LIBS+=" $($(tc-getPKG_CONFIG) libtirpc --libs)"

obviously the LIBS part will need tweaking based on your package.
-mike