please merge lib & lib64

[VictorEijkhout]

Your installation creates a lib64 directory with the actual libraries, and lib with only pkgconfig. This is very confusing, trips up my scripts, et cetera.

Is there a reason not to merge this?

[VictorEijkhout]

pkgconfig.cmake:

set(pc_target ${pc_filename})
set(pc_link ${CMAKE_INSTALL_PREFIX}/lib/pkgconfig/p4est.pc)

but I have no idea where you generate the lib64 name.