MINOR: Use "500 Internal Server Error" for 500 error/status code message.

Internal Server Error is what is in RFC 2616/7231.
diff --git a/examples/errorfiles/500.http b/examples/errorfiles/500.http
index bb121e8..ebf7d47 100644
--- a/examples/errorfiles/500.http
+++ b/examples/errorfiles/500.http
@@ -1,9 +1,9 @@
-HTTP/1.0 500 Server Error

+HTTP/1.0 500 Internal Server Error

 Cache-Control: no-cache

 Connection: close

 Content-Type: text/html

 

-<html><body><h1>500 Server Error</h1>
+<html><body><h1>500 Internal Server Error</h1>
 An internal server error occured.
 </body></html>
 
diff --git a/src/hlua.c b/src/hlua.c
index 35fb717..bfb9c94 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -216,12 +216,12 @@
 static struct hlua_mem_allocator hlua_global_allocator;
 
 static const char error_500[] =
-	"HTTP/1.0 500 Server Error\r\n"
+	"HTTP/1.0 500 Internal Server Error\r\n"
 	"Cache-Control: no-cache\r\n"
 	"Connection: close\r\n"
 	"Content-Type: text/html\r\n"
 	"\r\n"
-	"<html><body><h1>500 Server Error</h1>\nAn internal server error occured.\n</body></html>\n";
+	"<html><body><h1>500 Internal Server Error</h1>\nAn internal server error occured.\n</body></html>\n";
 
 /* These functions converts types between HAProxy internal args or
  * sample and LUA types. Another function permits to check if the
diff --git a/src/proto_http.c b/src/proto_http.c
index f7f7545..8bc1636 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -196,12 +196,12 @@
 	"<html><body><h1>429 Too Many Requests</h1>\nYou have sent too many requests in a given amount of time.\n</body></html>\n",
 
 	[HTTP_ERR_500] =
-	"HTTP/1.0 500 Server Error\r\n"
+	"HTTP/1.0 500 Internal Server Error\r\n"
 	"Cache-Control: no-cache\r\n"
 	"Connection: close\r\n"
 	"Content-Type: text/html\r\n"
 	"\r\n"
-	"<html><body><h1>500 Server Error</h1>\nAn internal server error occured.\n</body></html>\n",
+	"<html><body><h1>500 Internal Server Error</h1>\nAn internal server error occured.\n</body></html>\n",
 
 	[HTTP_ERR_502] =
 	"HTTP/1.0 502 Bad Gateway\r\n"