Add mseal(2) wrapper.

Change-Id: I053b2d570cd5750285fc20e9e237e04d59778bf5
diff --git a/libc/libc.map.txt b/libc/libc.map.txt
index ffd5d1e..8bb84eb 100644
--- a/libc/libc.map.txt
+++ b/libc/libc.map.txt
@@ -670,6 +670,7 @@
     mprotect;
     mrand48;
     mremap;
+    mseal; # introduced=36
     msync;
     munlock;
     munlockall;