[tlbuild] Test failures for dvipdmfx on OpenBSD

[Hironobu Yamashita]

Hi Mojca & Karl,

> dvipdfmx non-deterministic behaviour

Devs from Japan investigated this;

  * It crashes at cmap_read.c L.579
      MATCH_OP(tok1, "begincodespacerange")
  * The crash occurs when the size of tok1->data is smaller
    than strlen("begincodespacerange").
  * When you use strncmp instead of memcmp in
      #define MATCH_OP(t,n)
    at cmap_read.c L.405, the crash will not happen.
    OTOH, it may match longer strings such as "begincodespacerangeeeee".
  * FYI, t1_load.c L.93 uses strncmp in a similar function MATCH_OP(t,n).

Best,
Hironobu