Fix buildsys

These commits fix and improve the build system. The first commit updates some m4 files to the latest. The second patch is the most important part: Without it, it is impossible to compile float (I am really surprised that apparently elsewhere it still compiled -- without this commit, I couldn't compile float on either Mac OS X or Linux). The third patch was added because clearly the Makefile.in files in the repository had been generated with the "foreign" flag, thus running "autoreconf" produced a diff. 

The last few patches remove some generated files from the repository (indeed, some of them were symlinks, which is a bad idea anyway, as they won't work across systems), and adjust .gitignore accordingly.