libc.map.txt: add a version for API 36.

Even if we're not doing letters any more, there was value to having a version just for keeping related things together.

Change-Id: Ide89fcf76da1bf743079e52cd7cb06490d16eb1e
diff --git a/libc/libc.map.txt b/libc/libc.map.txt
index 0d2e42f..d8636a2 100644
--- a/libc/libc.map.txt
+++ b/libc/libc.map.txt
@@ -591,7 +591,6 @@
     killpg;
     klogctl;
     labs;
-    lchmod; # introduced=36
     lchown;
     lcong48; # introduced=23
     ldexp;
@@ -671,7 +670,6 @@
     mprotect;
     mrand48;
     mremap;
-    mseal; # introduced=36
     msync;
     munlock;
     munlockall;
@@ -846,7 +844,6 @@
     pwrite;
     pwrite64;
     qsort;
-    qsort_r; # introduced=36
     quick_exit;
     raise;
     rand;
@@ -955,7 +952,6 @@
     setvbuf;
     setxattr;
     shutdown;
-    sig2str; # introduced=36
     sigaction;
     sigaddset;
     sigaltstack;
@@ -998,7 +994,6 @@
     stdout; # var introduced=23
     stpcpy;
     stpncpy;
-    str2sig; # introduced=36
     strcasecmp;
     strcasecmp_l; # introduced=23
     strcasestr;
@@ -1613,6 +1608,15 @@
     __system_properties_zygote_reload; # apex
 } LIBC_U;
 
+LIBC_36 { # introduced=36
+  global:
+    lchmod;
+    mseal;
+    qsort_r;
+    sig2str;
+    str2sig;
+} LIBC_V;
+
 LIBC_PRIVATE {
   global:
     __accept4; # arm x86