linker: add dlvsym(3)

This changes implements dlvsym - dlsym for versioned symbols.

Bug: http://b/22865643
Change-Id: Ic90a60d512104261a1416c43f9100f0d88e3b46f
diff --git a/libdl/libdl.mips64.map b/libdl/libdl.mips64.map
index 3535774..a8c98da 100644
--- a/libdl/libdl.mips64.map
+++ b/libdl/libdl.mips64.map
@@ -17,6 +17,7 @@
   global:
     android_init_namespaces;
     android_create_namespace;
+    dlvsym;
 } LIBC;
 
 LIBC_PRIVATE {