Control where win32 DLLs get installed.

Control where win32 DLLs get installed.

* libltdl/config/general.m4sh (func_normal_abspath): New function.
(func_relative_path): Likewise.
* libltdl/config/ltmain.m4sh (func_mode_help): Document "-bindir".
(func_mode_link): Accept new "-bindir" option and use it, if
supplied, to place Windows DLLs.
* tests/bindir.at: New file for install tests using "-bindir".
* Makefile.am (TESTSUITE_AT): Add bindir.at.
* doc/libtool.texi (Link Mode): Update documentation.
* NEWS, THANKS: Update.

Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>