add posix_close, accepted for inclusion in the next issue of POSIX

this is purely a wrapper for close since Linux does not support EINTR
semantics for the close syscall.

include/unistd.h

@@ -35,6 +35,7 @@ extern "C" {
 int pipe(int [2]);
 int pipe2(int [2], int);
 int close(int);
+int posix_close(int, int);
 int dup(int);
 int dup2(int, int);
 int dup3(int, int, int);
@@ -200,6 +201,8 @@ int eaccess(const char *, int);
 #define off64_t off_t
 #endif
 
+#define POSIX_CLOSE_RESTART     0
+
 #define _XOPEN_VERSION          700
 #define _XOPEN_UNIX             1
 #define _XOPEN_ENH_I18N         1

src/unistd/posix_close.c

@@ -0,0 +1,6 @@
+#include <unistd.h>
+
+int posix_close(int fd, int flags)
+{
+	return close(fd);
+}