liblog: add __android_log_is_loggable()

- Add new liblog API __android_log_is_loggable(prio, tag, def)
- future plan to integrate this into the runtime checks and into
  the logd daemon for filtration. Inert for now.

Bug: 17760225
Change-Id: I16395b4d42acc08f0209f55a1cbf87b0b2112898
diff --git a/liblog/log_read.c b/liblog/log_read.c
index 2f21a5d..dbed886 100644
--- a/liblog/log_read.c
+++ b/liblog/log_read.c
@@ -34,7 +34,11 @@
 /* branchless on many architectures. */
 #define min(x,y) ((y) ^ (((x) ^ (y)) & -((x) < (y))))
 
+#if (defined(USE_MINGW) || defined(HAVE_WINSOCK))
+#define WEAK static
+#else
 #define WEAK __attribute__((weak))
+#endif
 #ifndef __unused
 #define __unused __attribute__((unused))
 #endif