Add a few new source files to libc++, in particular the implementation

part of std::random_shuffle. These were split off at some point by
upstream, but I forgot to add them to our Makefile.

This should allow some ports which use std::random_shuffle to correctly
link again.

Reported by:	thierry
PR:		248795
MFC after:	6 weeks
X-MFX-With:	r364284

lib/libc++/Makefile

@@ -16,6 +16,8 @@ SHLIB_LDSCRIPT=	libc++.ldscript
 
 SRCS+=		algorithm.cpp
 SRCS+=		any.cpp
+SRCS+=		atomic.cpp
+SRCS+=		barrier.cpp
 SRCS+=		bind.cpp
 SRCS+=		charconv.cpp
 SRCS+=		chrono.cpp
@@ -38,6 +40,7 @@ SRCS+=		mutex_destructor.cpp
 SRCS+=		new.cpp
 SRCS+=		optional.cpp
 SRCS+=		random.cpp
+SRCS+=		random_shuffle.cpp
 SRCS+=		regex.cpp
 SRCS+=		shared_mutex.cpp
 SRCS+=		stdexcept.cpp