Revert past commits

Revert past commits

I accidentally pushed my work-in-progress branch... revert that.  Sorry
for the noise :(.

The list of commits reverted are:

    ae2a50a9ae15 attempt to revamp to the CU/TU list
    e9386435c94f gdb/dwarf: print DWARF CUs/TUs in "maint print objfiles"
    6cbd64aa3eb0 gdb/dwarf: add dwarf_source_language_name
    32a187da7622 libiberty: move DW_LANG_* definitions to dwarf2.def
    b3fa38aef59d gdb/dwarf: move index unit vectors to debug names reader and use them
    30ba74418982 gdb/dwarf: track comp and type units count
    bedb4e09f292 gdb/dwarf: remove unnecessary braces
    b4f18de12c77 gdb/dwarf: use ranged for loop in some pots

Change-Id: I80aed2847025f5b15c16c997680783b39858a703