Improve system calls

- Wrap clock_getres()
- Wrap sched_setscheduler()
- Make sleep() api conformant
- Polyfill sleep() using select()
- Improve clock_gettime() polyfill
- Make nanosleep() POSIX conformant
- Slightly improve some DNS functions
- Further strengthen pledge() sandboxing
- Improve rounding of timeval / timespec
- Allow layering of pledge() calls on Linux
- Polyfill sched_yield() using select() on XNU
- Delete more system constants we probably don't need

libc/dns/dns.h

@@ -37,6 +37,15 @@
 #define AI_ADDRCONFIG  0x0400
 #define AI_V4MAPPED    0x0800
 
+#define NI_NUMERICSCOPE 0
+#define NI_NUMERICHOST  1
+#define NI_NUMERICSERV  2
+#define NI_NOFQDN       4
+#define NI_NAMEREQD     8
+#define NI_DGRAM        16
+#define NI_MAXSERV      32
+#define NI_MAXHOST      1025
+
 #if !(__ASSEMBLER__ + __LINKER__ + 0)
 COSMOPOLITAN_C_START_