Portability fixes.


BUILD/compile-alpha-debug:
  Update to newer version
libmysqld/lib_vio.c:
  dbug_assert -> DBUG_ASSERT
mysql-test/r/symlink.result:
  Update for new tests
mysql-test/t/symlink.test:
  Update for new test format
mysys/mf_iocache2.c:
  Fixed bug when reading in old buffer
sql-bench/test-transactions.sh:
  Update with delete tests
sql/mysqld.cc:
  Updates for amiga
sql/sql_string.cc:
  Fix typo
sql/stacktrace.c:
  Portability fix