make failed due to absence of -lm

[lambday]

Hi, I have been trying to install LibSVM-Plus because I need SVDD. When trying to install using

# from libsvm+ root directory
$ ./autogen.sh
$ mkdir build && cd build && ../configure && make -j4

I ran into errors like

/usr/bin/ld: svm.o: undefined reference to symbol 'exp@@GLIBC_2.2.5'

Using configure LIBS=-lm fixed the problem. Also, the README seems outdated. Shall I just update it and send a PR?

Great work by the way :)