warning: 'inline' is not at beginning of declaration ?

In an attempt to build a kernel with -Wextra gives a number
of warnings for

	'inline' is not at beginning of declaration

(in tcp_input.c, as an example).

Is there any interest in trying to fix these ?

	HEAD/sys/netinet/tcp_input.c:218: warning: 'inline' is not at beginning of declaration
	HEAD/sys/netinet/tcp_input.c:224: warning: 'inline' is not at beginning of declaration
	HEAD/sys/netinet/tcp_input.c:226: warning: 'inline' is not at beginning of declaration
	HEAD/sys/netinet/tcp_input.c:227: warning: 'inline' is not at beginning of declaration
	HEAD/sys/netinet/tcp_input.c:228: warning: 'inline' is not at beginning of declaration
	HEAD/sys/netinet/tcp_input.c:248: warning: 'inline' is not at beginning of declaration
	HEAD/sys/netinet/tcp_input.c:266: warning: 'inline' is not at beginning of declaration
	HEAD/sys/netinet/tcp_input.c:298: warning: 'inline' is not at beginning of declaration
	HEAD/sys/netinet/tcp_input.c:388: warning: 'inline' is not at beginning of declaration
	HEAD/sys/netinet/tcp_input.c:440: warning: 'inline' is not at beginning of declaration

On a related topic, do we have any mechanism to provide
per-subdir or per-file CFLAGS during kernel builds ?
I tried to put a Makefile.inc in a subdirectory but it
did not help.

cheers
luigi