Convert file name to toolchain format when invoking $NM.

Convert file name to toolchain format when invoking $NM.

* libltdl/config/ltmain.m4sh (func_generate_dlsyms)
(func_win32_libid, func_cygming_gnu_implib_p)
(func_cygming_ms_implib_p): When using the name lister to find
symbols in files, convert the file names to a format appropriate
for the tool. Fixes testsuite issues in mdemo-static-make.test
and mdemo-make.test when doing a cross from Cygwin/Wine to MinGW
using MinGW native tools (a.k.a. a "faked" cross).

Signed-off-by: Peter Rosin <peda@lysator.liu.se>