spa: add spa_atob() to convert a string to a boolean

This replaces the manual check for "true" and some (inconsistent) return value
of atoi. All those instances now require either "true" or "1" to parse as
true, any other value (including NULL) is boolean false.

spa/include/spa/utils/string.h

@@ -82,6 +82,17 @@ static inline bool spa_atoi32(const char *str, int32_t *val, int base)
 	return true;
 }
 
+/**
+ * Convert \a str to a boolean. Allowed boolean values are "true" and a
+ * literal "1", anything else is false.
+ *
+ * \return true on success, false otherwise
+ */
+static inline bool spa_atob(const char *str)
+{
+	return spa_streq(str, "true") || spa_streq(str, "1");
+}
+
 #ifdef __cplusplus
 }  /* extern "C" */
 #endif