Switch to upstream sleep(3) and usleep(3).
Also fix the signature of usleep, and the definition of useconds_t which
should be unsigned, as the 'u' in its name implies.
This patch also cleans up the existing FreeBSD hacks by moving the libm
stuff from <sys/cdefs.h> to a libm-private header, and adding comments
about the hacks we use to build FreeBSD source.
Change-Id: Ibe5067a380502df94a0a3a7901969b35411085b6
diff --git a/libc/include/unistd.h b/libc/include/unistd.h
index 91b0d8d..29758f5 100644
--- a/libc/include/unistd.h
+++ b/libc/include/unistd.h
@@ -159,7 +159,7 @@
extern int pause(void);
extern unsigned int alarm(unsigned int);
extern unsigned int sleep(unsigned int);
-extern int usleep(unsigned long);
+extern int usleep(useconds_t);
extern int gethostname(char *, size_t);