Autoconf for CLAPACK

[edrosten]

Would you consider adding an autoconf build script for CLAPACK?

I've attached a patch which adds an autoconf build system for CLAPACK.

Autoconf for CLAPACK is useful becasue it allows for easy compiling and in particular very easy cross compiling. Currently, cross compiling CLAPACK from the makefiles is very difficult and involved a lot of makefile editing, and by-hand creation of some of the generated indlude files.

I haven't used automake. Just run "autoconf" to generate the configure script.

I've also made the minimal possible changes to the source code (minor changes in second.c and dsecnd.c only).

The patch is only tested for my configuration (building native 64 bit on Linux and cross compiling to 32 bit MinGW which breaks quite a lot of assumptions that the old build system used).