gdb/cp-namespace.c: Fix assert failure caused by malformed user input

gdb/cp-namespace.c: Fix assert failure caused by malformed user input

When debugging C++ programs, it is possible to trigger a spurious assert
failure when attempting to set a breakpoint on a malformed symbol name.
Names of the form 'A>::B' and 'A)::B' trigger this assert failure in
cp_lookup_bare_symbol:

    $ gdb gdb
    [...]
    (gdb) br test>::assert
    Function "test>::assert" not defined.
    Make breakpoint pending on future shared library load? (y or [n]) y
    Breakpoint 1 (test>::assert) pending.
    (gdb) start
    [...]
    cp-namespace.c:181: internal-error: cp_lookup_bare_symbol: Assertion `strstr (name, "::") == NULL' failed.
    A problem internal to GDB has been detected,
    further debugging may prove unreliable.
    ----- Backtrace -----
    0x5217e2 gdb_internal_backtrace_1
            /home/amerey/binutils-gdb/gdb/bt-utils.c:122
    0x521885 _Z22gdb_internal_backtracev
            /home/amerey/binutils-gdb/gdb/bt-utils.c:168
    0xaf8303 internal_vproblem
            /home/amerey/binutils-gdb/gdb/utils.c:396
    0xaf86be _Z15internal_verrorPKciS0_P13__va_list_tag
            /home/amerey/binutils-gdb/gdb/utils.c:476
    0xccdb3f _Z18internal_error_locPKciS0_z
            /home/amerey/binutils-gdb/gdbsupport/errors.cc:58
    0x5dded9 cp_lookup_bare_symbol
            /home/amerey/binutils-gdb/gdb/cp-namespace.c:181
    0x5de39d cp_lookup_symbol_in_namespace
            /home/amerey/binutils-gdb/gdb/cp-namespace.c:328
    [...]

Currently this assert is skipped if the symbol name contains '<' or '('.
Fix this spurious failure by also skipping the assert when the symbol
name contains '>' or ')'.

Regression tested on F38 x86_64.

Approved-By: Tom Tromey <tom@tromey.com>