ccache: use install_symlink
pigz: use install_symlink
putmail: use install_symlink
vim: use install_symlink
qrupdate.rb,slicot.rb: improved BLAS/LAPACK support.

qrupdate.rb: added OpenBLAS option. Compiled with -ff2c flag for -framework vecLib to ensure compatibility.
slicot.rb: removed all mention of BLAS/LAPACK, because only the static library is built.