gdb: Remove arm-symbianelf support

gdb: Remove arm-symbianelf support

Since it has gone from bfd/.

	* arm-symbian-tdep.c: Delete.
	* NEWS: Mention arm-symbian removal.
	* Makefile.in: Remove arm-symbian-tdep entries.
	* configure.tgt: Remove arm*-*-symbianelf*.
	* doc/gdb.texinfo: Remove mention of SymbianOS.
	* osabi.c (gdb_osabi_names): Remove "Symbian".
	* osabi.h (enum gdb_osabi): Remove GDB_OSABI_SYMBIAN.
	* testsuite/gdb.base/ending-run.exp: Remove E32Main handling.
	* testsuite/gdb.ada/catch_ex_std.exp: Remove arm*-*-symbianelf*
	handling.
	* testsuite/gdb.base/dup-sect.exp: Likewise.
	* testsuite/gdb.base/long_long.exp: Likewise.
	* testsuite/gdb.base/solib-weak.exp: Likewise.
	* testsuite/gdb.guile/scm-section-script.exp: Likewise.
	* testsuite/gdb.python/py-section-script.exp: Likewise.
	* testsuite/lib/dwarf.exp: Likewise.
	* testsuite/lib/gdb.exp: Likewise.