* deffile.h: New file; direct support for PE DLLs
* deffilep.y: New file; direct support for PE DLLs
* emultempl/pe.em: add direct support for PE DLLs
* configure.tgt: allow target-specific extra files
* configure.in: allow target-specific extra files
* ldlang.c (lang_add_assignment): return the assignment so that
one can change the value later based on the object files (pe-dll
DEF files do this)
* ldint.texinfo: add section for emulation walkthrough
