Merge remote-tracking branch 'origin/vm/page-swap-synch' into vm/virtual-memory/saleh

# Conflicts:
#	.gitlab-ci.yml
#	src/Makefile.build
#	src/threads/thread.c
#	src/userprog/exception.c
#	src/userprog/process.c
#	src/vm/frame.c
#	src/vm/page.c
#	src/vm/page.h
#	src/vm/stackgrowth.c
#	src/vm/stackgrowth.h

src/userprog/syscall.c

@@ -616,4 +616,4 @@ put_user (uint8_t *udst, uint8_t byte)
        : "=&a"(error_code), "=m"(*udst)
        : "q"(byte));
   return error_code != -1;
-}
+}