Include <strings.h> for the strncasecmp function.

diff --git a/src/command2esp.c b/src/command2esp.c
index 529342c99c5c5f52..c1acdb16a1ec2f1c 100644
--- a/src/command2esp.c
+++ b/src/command2esp.c
@@ -44,6 +44,7 @@ Maintenance=003?
 #include <cups/cups.h>
 #include <cups/sidechannel.h> //FlushBackChannel, and the side channel functions and constants
 #include "string.h"
+#include <strings.h>
 #include <ctype.h> 
 #include <fcntl.h> //files
 #include <time.h> //time functions used for debugging