Save a couple characters' allocation in esc_for_log

changes/less_alloc_for_esc

+ o Minor bugfixes
+   - Save a couple bytes in memory allocation every time we escape
+     certain characters in a string.  Patch from Florian Zumbiehl.

src/common/util.c

@@ -940,6 +940,9 @@ esc_for_log(const char *s)
       case '\\':
       case '\"':
       case '\'':
+      case '\r':
+      case '\n':
+      case '\t':
         len += 2;
         break;
       default: