Properly clean and ignore flat make binaries and libs

bin/package, src/cmd/INIT/package.sh:
- When running bin/package flat make clean, also clean the flat
  hierarchy binaries.

.gitignore:
- Ignore flat hierarchy binaries.

.gitignore

@@ -3,6 +3,41 @@ arch
 tgz
 lcl
 
+# Flat make libs, binaries, etc
+bin/.paths
+bin/ar
+bin/cc
+bin/crossexec
+bin/ditto
+bin/filter
+bin/hurl
+bin/iffe
+bin/ksh
+bin/mamake
+bin/mktest
+bin/ok/
+bin/proto
+bin/pty
+bin/ratz
+bin/regress
+bin/release
+bin/rt
+bin/shcomp
+bin/suid_exec
+fun/
+include/
+lib/file/
+lib/lib/
+lib/libast.a
+lib/libcmd.a
+lib/libdll.a
+lib/libshell.a
+lib/libsum.a
+lib/make/
+lib/package/gen/
+lib/probe/
+man/
+
 # This one keeps changing its license header, causing git to show an
 # uncommitted file. It's always re-copied anyway, and not for direct
 # invocation, so exclude. The source file is: src/cmd/INIT/execrate.sh