dwarf.h: Add DW_LANG_C11, DW_LANG_C_plus_plus_11 and DW_LANG_C_plus_plus_14.

dwarf.h: Add DW_LANG_C11, DW_LANG_C_plus_plus_11 and DW_LANG_C_plus_plus_14.

The following patch is needed to recognize the new DW_LANG constants
that GCC 5 might emit as implemented by this GCC patch:
https://gcc.gnu.org/ml/gcc-patches/2014-11/msg02852.html

Also added to https://fedorahosted.org/elfutils/wiki/DwarfExtensions

GCC 5 can emit these new DWARFv5 draft language constants. Handle them in
dwarf_aggregate_size and dwarf_getfuncs. Also handle DW_LANG_Go in
dwarf_aggregate_size (lower bound for array is zero for Go).

Signed-off-by: Mark Wielaard <mjw@redhat.com>