Add autoreconf to README

[rhysmeister]

Probably worth mentioning you need to execute...

autoreconf

in the lib_mysqludf_skeleton to generate the configure script.

Cheers,

Rhys

[skroczek]

I needed to add

 $ autoreconf -i -f

because of the error

configure.ac:12: error: required file 'config/compile' not found
configure.ac:12: 'automake --add-missing' can install 'compile'
autoreconf: automake failed with exit status: 1