[ADMB Users] using mingw32 cross compiler.

[dave fournier]

It would save a lot of time if someone with nothing useful to do would 
modify the makefiles
to enable the use of the mingw 32 and 64 bit cross compilers. these run 
fine on my
Ubuntu.   Three things are necessary

for the 32 bit version

  CC=i586-mingw32msvc-gcc
  CXX=i586-mingw32msvc-g++

CC=amd64-mingw32msvc-gcc
CXX=amd64-mingw32msvc-g++

The gotcha is in the archiver.
One needs

AR=i586-mingw32msvc-ar
for 32 bit version
and
AR=amd64-mingw32msvc-ar
for 64 bit version

but in the makefiles in the subdirectories the macro AR is not used.

So one needs to put AR=ar
at the top of each makefile and change

    ar -rs

to

   $AR -rs

Without this change it uses the Linux ar which creates
libraries in a different format so that when you try and
link nothing works.