libuv: misc: add function to get CPU affinity mask size

Implement it on Linux, FreeBSD, and Windows for now, and return
UV_ENOTSUP on other platforms.

Backported from upstream libuv PR 1527, scheduled for inclusion
in libuv 2.0.

Utilities/cmlibuv/include/uv.h

@@ -1094,6 +1094,7 @@ UV_EXTERN uv_pid_t uv_os_getppid(void);
 
 UV_EXTERN int uv_cpu_info(uv_cpu_info_t** cpu_infos, int* count);
 UV_EXTERN void uv_free_cpu_info(uv_cpu_info_t* cpu_infos, int count);
+UV_EXTERN int uv_cpumask_size(void);
 
 UV_EXTERN int uv_interface_addresses(uv_interface_address_t** addresses,
                                      int* count);

Utilities/cmlibuv/src/unix/core.c

@@ -40,6 +40,7 @@
 #include <sys/uio.h> /* writev */
 #include <sys/resource.h> /* getrusage */
 #include <pwd.h>
+#include <sched.h>
 
 #ifdef __sun
 # include <netdb.h> /* MAXHOSTNAMELEN on Solaris */
@@ -63,6 +64,8 @@
 # include <sys/sysctl.h>
 # include <sys/filio.h>
 # include <sys/wait.h>
+# include <sys/param.h>
+# include <sys/cpuset.h>
 # define UV__O_CLOEXEC O_CLOEXEC
 # if defined(__FreeBSD__) && __FreeBSD__ >= 10
 #  define uv__accept4 accept4
@@ -1340,6 +1343,15 @@ int uv_os_gethostname(char* buffer, size_t* size) {
 }
 
 
+int uv_cpumask_size(void) {
+#if defined(__linux__) || defined(__FreeBSD__)
+  return CPU_SETSIZE;
+#else
+  return UV_ENOTSUP;
+#endif
+}
+
+
 uv_os_fd_t uv_get_osfhandle(int fd) {
   return fd;
 }

Utilities/cmlibuv/src/win/core.c

@@ -603,3 +603,7 @@ int uv__socket_sockopt(uv_handle_t* handle, int optname, int* value) {
 
   return 0;
 }
+
+int uv_cpumask_size(void) {
+  return (int)(sizeof(DWORD_PTR) * 8);
+}