Coverity 1038111: fix local overrun of a string in app layer proto detect setup code.

src/detect-content.c

@@ -270,7 +270,7 @@ DetectContentData *DetectContentParse (char *contentstr)
 
 DetectContentData *DetectContentParseEncloseQuotes(char *contentstr)
 {
-    char str[strlen(contentstr) + 2];
+    char str[strlen(contentstr) + 3]; // 2 for quotes, 1 for \0
 
     str[0] = '\"';
     memcpy(str + 1, contentstr, strlen(contentstr));