libc: move rfork_thread(3) to libsys

rfork_thread(3) is assembly that makes syscalls directly and uses
cerror so it belongs in libsys.

Reviewed by:	kib, emaste, imp
Pull Request:	https://github.com/freebsd/freebsd-src/pull/908

lib/libc/amd64/gen/Makefile.inc

@@ -1,5 +1,5 @@
 
-SRCS+=	_setjmp.S rfork_thread.S setjmp.S sigsetjmp.S \
+SRCS+=	_setjmp.S setjmp.S sigsetjmp.S \
 	fabs.S \
 	infinity.c ldexp.c makecontext.c signalcontext.c \
 	flt_rounds.c fpgetmask.c fpsetmask.c fpgetprec.c fpsetprec.c \

lib/libc/gen/Makefile.inc

@@ -279,7 +279,6 @@ MAN+=	alarm.3 \
 	raise.3 \
 	rand48.3 \
 	readpassphrase.3 \
-	rfork_thread.3 \
 	scandir.3 \
 	sem_destroy.3 \
 	sem_getvalue.3 \

lib/libc/i386/gen/Makefile.inc

@@ -1,4 +1,4 @@
 
 SRCS+=	_ctx_start.S _setjmp.S fabs.S \
 	flt_rounds.c infinity.c ldexp.c makecontext.c \
-	rfork_thread.S setjmp.S signalcontext.c sigsetjmp.S
+	setjmp.S signalcontext.c sigsetjmp.S

lib/libsys/Makefile.sys

@@ -365,6 +365,7 @@ MAN+=	abort2.2 \
 
 MAN+= \
 	lockf.3 \
+	rfork_thread.3 \
 	sleep.3 \
 	usleep.3
 

lib/libsys/amd64/Makefile.sys

@@ -2,6 +2,7 @@ SRCS+=	\
 	amd64_get_fsbase.c \
 	amd64_get_gsbase.c \
 	amd64_set_fsbase.c \
-	amd64_set_gsbase.c
+	amd64_set_gsbase.c \
+	rfork_thread.S
 
 MDASM=	vfork.S cerror.S getcontext.S

lib/libsys/i386/Makefile.sys

@@ -1,6 +1,7 @@
 SRCS+=	i386_get_fsbase.c i386_get_gsbase.c i386_get_ioperm.c i386_get_ldt.c \
 	i386_set_fsbase.c i386_set_gsbase.c i386_set_ioperm.c i386_set_ldt.c \
-	i386_clr_watch.c i386_set_watch.c i386_vm86.c
+	i386_clr_watch.c i386_set_watch.c i386_vm86.c \
+	rfork_thread.S
 
 MDASM=	vfork.S cerror.S getcontext.S syscall.S