Eliminate uses of NAMES_HAVE_UNDERSCORE, using

Eliminate uses of NAMES_HAVE_UNDERSCORE, using
bfd_get_symbol_leading_char instead.

* coffread.c (EXTERNAL_NAME):  New macro for removing possible
leading character from names.
(read_coff_symtab):  Use BFD's FILE *, don't open a second one.
(read_coff_symtab):  Complain() about .bb/.eb mismatch, don't error().
(process_coff_symbol, coff_read_struct_type, coff_read_enum_type):
Replace NAMES_HAVE_UNDERSCORE with EXTERNAL_NAME.

* kdb-start.c (main):  Remove NAMES_HAVE_UNDERSCORE.
* minsyms.c (install_minimal_symbols):  Replace NAMES_HAVE_UNDERSCORE.
Remove SOME_NAMES_HAVE_DOT support (apparently unused).
* partial-stab.h:  Replace NAMES_HAVE_UNDERSCORE.
* solib.c:  Replace NAMES_HAVE_UNDERSCORE.
* stabsread.h:  Remove NAMES_HAVE_UNDERSCORE and HASH_OFFSET.
* symfile.c (syms_from_objfile):  Insert debugging check to test
NAMES_HAVE_UNDERSCORE setting against the BFD support.  FIXME,
remove this (and all tm-*.h NAMES_HAVE_UNDERSCORE) soon.

* doc/gdbint.texinfo (Host Conditionals):  Remove
NAMES_HAVE_UNDERSCORE, SOME_NAMES_HAVE_DOT, document
MEM_FNS_DECLARED.
(Target Conditionals):  Remove all of the above.