Fixed a nasty layering violation in the edis source

Fixed a nasty layering violation in the edis source
code.  It used to #include the enhanced disassembly
information for the targets it supported straight
out of lib/Target/{X86,ARM,...} but now it uses a
new interface provided by MCDisassembler, and (so
far) implemented by X86 and ARM.

Also removed hacky #define-controlled initialization
of targets in edis.  If clients only want edis to
initialize a limited set of targets, they can set
--enable-targets on the configure command line.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101179 91177308-0d34-0410-b5e6-96231b3b80d8