StatsD: Add res_statsd compatibility

Added a new api to res_statsd.c to allow it to receive a
character pointer for the value argument. This allows for a
'+' and a '-' to easily be sent with the value.

ASTERISK-25419
Reported By: Ashley Sanders

Change-Id: Id6bb53600943d27347d2bcae26c0bd5643567611

include/asterisk/statsd.h

@@ -39,6 +39,22 @@
 /*! Events over time. Sorta like increment-only counters. */
 #define AST_STATSD_METER "m"
 
+/*!
+ * \brief Send a stat to the configured statsd server.
+ *
+ * This function uses a character argument for value instead of
+ * an intmax_t argument. This is designed to be simpler to use for
+ * updating a current value rather than resetting it.
+ *
+ * \param metric_name String (UTF-8) name of the metric.
+ * \param type_str Type of metric to send.
+ * \param value Value to send.
+ * \param sample_rate Percentage of samples to send.
+ * \since 13
+ */
+AST_OPTIONAL_API(void, ast_statsd_log_string, (const char *metric_name,
+	const char *metric_type, const char *value, double sample_rate), {});
+
 /*!
  * \brief Send a stat to the configured statsd server.
  *