Add strtof_l and strtod_l.

libc++ needs these now. Add shims to match the others.

Test: make checkbuild tests
Bug: http://b/31639993
Change-Id: Ifec6c32099145d8d3d1a5639a4809e5e9f553c33
diff --git a/libc/libc.map.txt b/libc/libc.map.txt
index 19fdb4b..1fba8ee 100644
--- a/libc/libc.map.txt
+++ b/libc/libc.map.txt
@@ -1331,6 +1331,10 @@
     sigpause; # future
     sigrelse; # future
     sigset; # future
+    strtod_l; # future
+    strtof_l; # future
+    strtol_l; # future
+    strtoul_l; # future
     sync_file_range; # future
     towctrans; # future
     towctrans_l; # future