* dlltool.c: Include <assert.h>.

* dlltool.c: Include <assert.h>.
(PREFIX_ALIAS_BASE): Define.
(struct export): Add member import_name;
(def_exports): Set import_name.
(make_one_lib_file): Remove prefix alias code, use import_name in .idata$6.
(gen_lib_file): Create and delete aliases.

* binutils-all/alias.def: New file.
* binutils-all/dlltool.exp: Two new -p tests.
* config/default.exp (dlltool_gas_flag): New variable.
Copy gas and lds executables into tmpdir/gas directory rather than making
symlinks which might not be supported by the host OS.
Attempt to handle the case where the host OS does not use the .exe extension
but the target OS does.
* lib/utils-lib.exp (exe_ext): New procedure.