Add some new features to libc.

.gitattributes

libc/include/close.h

libc/include/open.h

libc/include/stdint.h

libc/include/stdlib.h

libc/include/syscall.h

libc/src/Makefile.in

libc/src/close.c

libc/src/open.c

libc/src/stdlib.c