Remove LBTT.

* configure.ac: Detect lbtt using AC_CHECK_PROG.
* m4/lbtt.m4: Delete.
* lbtt/: Remove directory.
* Makefile.am, README: Adjust.

m4/lbtt.m4

@@ -1,40 +0,0 @@
-AC_DEFUN([AX_CHECK_LBTT], [
-  AC_ARG_WITH([included-lbtt],
-	      [AC_HELP_STRING([--with-included-lbtt],
-			      [use the LBTT program inclued here])])
-  AS_IF([AM_RUN_LOG([lbtt-translate --version | grep 1.2.1a])],
-	[need_included_lbtt=no],
-	[need_included_lbtt=yes])
-
-  if test "$need_included_lbtt" = yes; then
-     if test "$with_included_lbtt" = no; then
-       AC_MSG_WARN([Cannot find lbtt, needed for test-suite and benchmarks.
-Please install lbtt first, or configure with --with-included-lbtt.])
-     else
-       with_included_lbtt=yes
-     fi
-  fi
-
-  if test "$with_included_lbtt" = yes;  then
-     LBTT='${top_builddir}/lbtt/src/lbtt'
-     LBTT_TRANSLATE='${top_builddir}/lbtt/src/lbtt-translate'
-  else
-     LBTT=lbtt
-     LBTT_TRANSLATE=lbtt-translate
-  fi
-
-  # We always configure lbtt, even if it is not built to ensure it
-  # gets distributed properly.  However, when someone uses
-  # --without-included-lbtt explicitely, we assume he might be trying
-  # to build Spot on a system where lbtt cannot build (e.g. MinGW) and
-  # where lbtt/configure will fail.  So we don't run the sub-configure
-  # only in this case.  On such a setup, "make distcheck" will break,
-  # but so probably isn't important.
-  if test "$with_included_lbtt" != no; then
-    AC_CONFIG_SUBDIRS([lbtt])
-  fi
-
-  AM_CONDITIONAL([WITH_INCLUDED_LBTT], [test "$with_included_lbtt" = yes])
-  AC_SUBST([LBTT])
-  AC_SUBST([LBTT_TRANSLATE])
-])