gdb: Remove support for old mangling schemes

An upcoming sync with gcc's libiberty [1] will remove support for old
mangling schemes (GNU v2, Lucid, ARM, HP and EDG).  It will remove the
cplus_demangle_opname function, so we need to get rid of its usages in
GDB (it's a GNU v2 specific function).

I think the changes are mostly relatively obvious, some hacks that were
necessary to support overloaded operators with GNU v2 mangling are not
needed anymore.

The change in stabsread.c is perhaps less obvious.  I think we could get
rid of more code in that region that is specific to old mangling
schemes, but I chose to do only the minimal changes required to remove
the cplus_demangle_opname uses.  There is also a detailed comment just
above that explaining how GNU v2 and v3 mangled symbols are handled, I
decided to leave it as-is, since I wasn't sure which part to remove,
change or leave there.

[1] The commit "Remove support for demangling GCC 2.x era mangling
schemes.", specifically.

gdb/ChangeLog:

	* gdbtypes.c (check_stub_method_group): Remove handling of old
	mangling schemes.
	* linespec.c (find_methods): Likewise.
	* stabsread.c (read_member_functions): Likewise.
	* valops.c (search_struct_method): Likewise.
	(value_struct_elt_for_reference): Likewise.
	* NEWS: Mention this change.

gdb/testsuite/ChangeLog:

	* gdb.cp/demangle.exp (test_gnu_style_demangling): Rename to...
	(test_gnuv3_style_demangling): ... this.
	(test_lucid_style_demangling): Remove.
	(test_arm_style_demangling): Remove.
	(test_hp_style_demangling): Remove.
	(do_tests): Remove calls to the above.

gdb/doc/ChangeLog:

	* gdb.texinfo (Print Settings): Remove mention of specific
	demangle-style values, just refer to the in-process help.

2 files changed, 9 insertions, 25 deletions

diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index 56d846c..9eb75e7 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,8 @@
+2019-01-09  Simon Marchi  <simon.marchi@ericsson.com>
+
+	* gdb.texinfo (Print Settings): Remove mention of specific
+	demangle-style values, just refer to the in-process help.
+
 2018-12-28  Tom Tromey  <tom@tromey.com>
 
 	* gdb.texinfo (Output Styling): New node.
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 4bca933..4a00834 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -10703,31 +10703,10 @@ or demangled form.
 @cindex symbol decoding style, C@t{++}
 @kindex set demangle-style
 @item set demangle-style @var{style}
-Choose among several encoding schemes used by different compilers to
-represent C@t{++} names.  The choices for @var{style} are currently:
-
-@table @code
-@item auto
-Allow @value{GDBN} to choose a decoding style by inspecting your program.
-This is the default.
-
-@item gnu
-Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
-
-@item hp
-Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
-
-@item lucid
-Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
-
-@item arm
-Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
-@strong{Warning:} this setting alone is not sufficient to allow
-debugging @code{cfront}-generated executables.  @value{GDBN} would
-require further enhancement to permit that.
-
-@end table
-If you omit @var{style}, you will see a list of possible formats.
+Choose among several encoding schemes used by different compilers to represent
+C@t{++} names.  If you omit @var{style}, you will see a list of possible
+formats.  The default value is @var{auto}, which lets @value{GDBN} choose a
+decoding style by inspecting your program.
 
 @item show demangle-style
 Display the encoding style currently in use for decoding C@t{++} symbols.