* coff-pe-read.c: New file - support reading of minimal symbols from a portable

* coff-pe-read.c: New file - support reading of minimal symbols from a portable
executable using the export table.
* coff-pe-read.h: New file.
* coffread.c: Include coff-pe-read.h.
(coff_symtab_read): Call read_pe_exported_syms iff no recognized debugging
symbols found.
* Makefile.in (SFILES): Add coff-pe-read.o.
(coff_pe_read_h): Define.
(COMMON_OBS): Add coff-pe-read.o.
(coffread.o): Add coff_pe_read_h dependency.
(coff-pe-read.o): New target.