Rewrite syslog(3) to use Android logging.

Since we don't have syslogd on Android and you can't run one on a non-rooted
device, it's more useful if syslog output just goes to the regular Android
logging system.

Bug: 14292866

(cherry picked from commit 3ad8ecb64e)

Change-Id: I3038855ca4f22532bf6d2c45d3f8028b866975f9

libc/bionic/libc_logging.cpp

@@ -378,6 +378,9 @@ static void out_vformat(Out& o, const char* format, va_list args) {
         } else if (c == '%') {
             buffer[0] = '%';
             buffer[1] = '\0';
+        } else if (c == 'm') {
+            // syslog-like %m for strerror(errno).
+            str = strerror(errno);
         } else {
             __assert(__FILE__, __LINE__, "conversion specifier unsupported");
         }