MXS-1262: Minor improvements to monitor journals

Moved 4 byte get/set into utils header. The byte packing functions in
maxscale/protocol/mysql.h should be migrated to the utils directory where
they can also be used by non-mysql code.

The temporary files are now generated with mkstemp. This will prevent
conflicts with multiple monitors operating on the same temporary journal
even though it is impossible in practice.

Added missing error messages to a couple of the functions.

include/maxscale/utils.h

@@ -123,4 +123,35 @@ bool mxs_mkdir_all(const char *path, int mask);
 
 long get_processor_count();
 
+/**
+ * Store a 4 byte integer
+ *
+ * @param ptr   Pointer where value is stored
+ * @param value Value to store
+ *
+ * @return The next byte after the stored value
+ */
+static inline uint8_t* mxs_set_byte4(uint8_t* ptr, uint32_t value)
+{
+    *ptr++ = value;
+    *ptr++ = (value >> 8);
+    *ptr++ = (value >> 16);
+    *ptr++ = (value >> 24);
+    return ptr;
+}
+
+/**
+ * Read a 4 byte integer
+ *
+ * @param ptr   Pointer where value is stored
+ * @param value Value to store
+ *
+ * @return The next byte after the stored value
+ */
+static inline uint32_t mxs_get_byte4(const uint8_t* ptr)
+{
+    return ((uint32_t) ptr[0]) | ((uint32_t) ptr[1] << 8) |
+        ((uint32_t) ptr[2] << 16) | ((uint32_t) ptr[3] << 24);
+}
+
 MXS_END_DECLS