libsys: relocate implementations and manpages

Remove core system call implementations and documentation to lib/libsys
and lib/libsys/<arch> from lib/libc/sys and lib/libc/<arch>/<sys>.
Update paths to allow libc to find them in their new home.

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

lib/libc/Makefile

@@ -5,6 +5,7 @@ SHLIBDIR?= /lib
 .include <src.opts.mk>
 
 LIBC_SRCTOP?= ${.CURDIR}
+LIBSYS_SRCTOP?=	${.CURDIR:H}/libsys
 
 # Pick the current architecture directory for libc. In general, this is named
 # MACHINE_CPUARCH, but some ABIs are different enough to require their own libc,
@@ -38,6 +39,7 @@ SHLIB_LDSCRIPT_LINKS=libxnet.so
 WARNS?=	2
 CFLAGS+=-I${LIBC_SRCTOP}/include -I${SRCTOP}/include
 CFLAGS+=-I${LIBC_SRCTOP}/${LIBC_ARCH}
+CFLAGS+=-I${LIBSYS_SRCTOP}/${LIBC_ARCH}
 .if ${MK_NLS} != "no"
 CFLAGS+=-DNLS
 .endif

lib/libc/powerpcspe/sys/Makefile.inc

@@ -1,2 +1,3 @@
 .PATH: ${LIBC_SRCTOP}/powerpc/sys
+.PATH: ${LIBSYS_SRCTOP}/powerpc
 .sinclude "${LIBC_SRCTOP}/powerpc/sys/Makefile.inc"

lib/libc/sys/Makefile.inc

@@ -1,6 +1,7 @@
 
 # sys sources
-.PATH: ${LIBC_SRCTOP}/${LIBC_ARCH}/sys ${LIBC_SRCTOP}/sys
+.PATH: ${LIBC_SRCTOP}/${LIBC_ARCH}/sys
+.PATH: ${LIBSYS_SRCTOP}/${LIBC_ARCH} ${LIBSYS_SRCTOP}
 
 # Include the generated makefile containing the *complete* list
 # of syscall names in MIASM.
@@ -109,7 +110,7 @@ SPSEUDO= ${PSEUDO:S/.o/.S/}
 
 SRCS+=	${SASM} ${SPSEUDO}
 
-SYM_MAPS+=	${LIBC_SRCTOP}/sys/Symbol.map
+SYM_MAPS+=	${LIBSYS_SRCTOP}/Symbol.sys.map
 
 # Generated files
 CLEANFILES+=	${SASM} ${SPSEUDO}