libcutils: compile with BOARD_VNDK_VERSION current

- moved __android_log_is_debuggable to a new public header
    (log_properties.h)
- vendor version of sched_policy uses ALOG* instead SLOG*

Test: (sanity) liblog-unit-tests
Test: (sanity) libcutils_test (noting b/b/32972117, two tests continue
  to fail)
Test: system/core as a whole makes with BOARD_VNDK_VERSION := current
  now with no problems.
Test: boots/works on internal marlin
Bug: 33241851

Change-Id: I5bc1f348dc0f0c8814bec5b5c3d2c52c825ab640
diff --git a/liblog/properties.c b/liblog/properties.c
index adf1900..c71cbcf 100644
--- a/liblog/properties.c
+++ b/liblog/properties.c
@@ -277,7 +277,7 @@
   return logLevel >= 0 && prio >= logLevel;
 }
 
-LIBLOG_ABI_PRIVATE int __android_log_is_debuggable() {
+LIBLOG_ABI_PUBLIC int __android_log_is_debuggable() {
   static uint32_t serial;
   static struct cache_char tag_cache;
   static const char key[] = "ro.debuggable";