static linking with oo2c oberon and gnu

One of the reasons I did not use oo2c compiler from the second branch is that it seemd impossible to compile statically linked binaries. And here is solution: libtool somehow drops the dependency of liboo2c to libm, and it is necessary to add '-lm' to the beginning of the variable 'dependency_libs' in the liboo2c.la libtool file.