Use library discovery for curses and panel

Summary:
This approach is tunable with custom paths for curses library.

It also detects whether there are requirements met.

I make use of it on NetBSD.

Patch by Kamil Rytarowski. Thanks!

Reviewers: clayborg

Subscribers: brucem, joerg, lldb-commits

Differential Revision: http://reviews.llvm.org/D14529

llvm-svn: 253151