comms/fldigi - fix build with clang

[shurd]

Summary

Fix hashmap macro test to compile with Clang

Commit with: MFH: 2014Q3

[skreuzer]

Approved. Thanks

[db]

I'd double check the configure.ac script here before sending fix upstream.
e.g. configure was modified to look for std::hash etc. to make it non specific to GCC or Clang since one of my earlier diffs I sent upstream was too specific.

Looking at configure.ac for example.

1. 1. std::hash or alternatives
2. Set ac_cv_std_hash or ac_cv_std_tr1_hash to yes/no
3. Define HAVE_STD_HASH or HAVE_STD_TR1_HASH in config.h
4. Substitute BOOST_CPPFLAGS and BOOST_LDFLAGS in Makefile
5. if falling back to Boost

AC_FLDIGI_HASH

That's my only concern. Approved of course.

[shurd]

Closed by commit rP361113 (authored by @shurd).