Hide internal __system_property_* functions

Bug: http://b/34114501
Test: bionic-unit-tests --gtest_filter=prop*
Change-Id: I1fc57b4ced6aaf841aad64e12e7696d25c2e027b
diff --git a/libc/libc.arm.map b/libc/libc.arm.map
index ebe249f..798b9c3 100644
--- a/libc/libc.arm.map
+++ b/libc/libc.arm.map
@@ -185,18 +185,11 @@
     __sym_ntop;
     __sym_ntos;
     __sym_ston;
-    __system_properties_init;
-    __system_property_area__; # var
-    __system_property_area_init; # introduced-arm=19 introduced-arm64=21 introduced-mips=19 introduced-mips64=21 introduced-x86=19 introduced-x86_64=21
-    __system_property_area_serial; # introduced=23
     __system_property_find;
     __system_property_foreach; # introduced-arm=19 introduced-arm64=21 introduced-mips=19 introduced-mips64=21 introduced-x86=19 introduced-x86_64=21
     __system_property_get;
     __system_property_read;
-    __system_property_serial; # introduced-arm=19 introduced-arm64=21 introduced-mips=19 introduced-mips64=21 introduced-x86=19 introduced-x86_64=21
     __system_property_set; # introduced-arm=12 introduced-arm64=21 introduced-mips=12 introduced-mips64=21 introduced-x86=12 introduced-x86_64=21
-    __system_property_set_filename; # introduced-arm=19 introduced-arm64=21 introduced-mips=19 introduced-mips64=21 introduced-x86=19 introduced-x86_64=21
-    __system_property_wait_any; # introduced-arm=19 introduced-arm64=21 introduced-mips=19 introduced-mips64=21 introduced-x86=19 introduced-x86_64=21
     __timer_create; # arm x86 mips
     __timer_delete; # arm x86 mips
     __timer_getoverrun; # arm x86 mips
@@ -1538,11 +1531,18 @@
 LIBC_DEPRECATED {
   global:
     __system_property_find_nth;
+    __system_property_wait_any;
 };
 
 LIBC_PLATFORM {
   global:
+    __system_properties_init;
+    __system_property_area__; # var
     __system_property_add;
+    __system_property_area_init;
+    __system_property_area_serial;
+    __system_property_serial;
+    __system_property_set_filename;
     __system_property_update;
     android_net_res_stats_get_info_for_net;
     android_net_res_stats_aggregate;