islink is posix now

Reference: /n/atom/patch/applied/islinkposix
Date: Tue Feb 23 04:28:31 CET 2016
Signed-off-by: quanstro@quanstro.net

--- /sys/include/ape/sys/stat.h	Tue Feb 23 04:28:20 2016
+++ /sys/include/ape/sys/stat.h	Tue Feb 23 04:28:22 2016
@@ -24,9 +24,7 @@
 };
 
 #define	S__MASK		     0170000
-#ifdef _RESEARCH_SOURCE
 #define S_ISLNK(m)	(((m)&S__MASK) == 0120000)
-#endif
 #define S_ISREG(m)	(((m)&S__MASK) == 0100000)
 #define S_ISDIR(m)	(((m)&S__MASK) == 0040000)
 #define S_ISCHR(m)	(((m)&S__MASK) == 0020000)