Fix --diable-shared --enable-plugins build breakage

Fix --diable-shared --enable-plugins build breakage

Directories that don't use libtool need to add -ldl (on most *nix
hosts) to provide dlopen for libbfd.

config/
	* plugins.m4 (AC_PLUGINS): If plugins are enabled, add -ldl to
	LIBS via AC_SEARCH_LIBS.
gdb/
	* acinclude.m4 (GDB_AC_CHECK_BFD): Don't add -ldl.
	* config.in: Regenerate.
sim/ppc/
	* configure.ac: Invoke AC_PLUGINS.
	* config.in: Regenerate.

and regen lots of configure files.