Remove unused file.

The thr_new(2) syscall is called through libc stub.  r154212 stopped
generating it for libthr but did not cleaned the unused remnants.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week

lib/libthr/support/Makefile.inc

@@ -1,29 +0,0 @@
-# $FreeBSD$
-
-.PATH: ${.CURDIR}/support ${SRCTOP}/lib/libc/gen ${SRCTOP}/lib/libc/string
-
-# libc must search machine_arch, then machine_cpuarch, but libthr has all its
-# code implemented in machine_cpuarch.  Cope.
-.if exists(${SRCTOP}/lib/libc/${MACHINE_ARCH}/sys)
-.PATH: ${SRCTOP}/lib/libc/${MACHINE_ARCH}/sys
-CFLAGS+= -I${SRCTOP}/lib/libc/${MACHINE_ARCH}
-.else
-.PATH: ${SRCTOP}/lib/libc/${MACHINE_CPUARCH}/sys
-CFLAGS+= -I${SRCTOP}/lib/libc/${MACHINE_CPUARCH}
-.endif
-
-SYSCALLS= thr_new
-
-SYSCALL_SRC=   ${SYSCALLS:S/$/.S/}
-SYSCALL_OBJ=   ${SYSCALLS:S/$/.pico/}
-
-${SYSCALL_SRC}:
-	printf '#include "SYS.h"\nRSYSCALL(${.PREFIX})\n' > ${.TARGET}
-
-LIBC_OBJS=
-
-SOBJS+=	thr_libc.pico
-CLEANFILES+= ${SYSCALL_SRC} ${SYSCALL_OBJ} ${LIBC_OBJS}
-
-thr_libc.pico: ${SYSCALL_OBJ} ${LIBC_OBJS}
-	${CC} -fPIC -nostdlib -o ${.TARGET} -r ${.ALLSRC}