Remove more unneeded tests and patches
    
    Changes in this commit:
    - Remove gdb-bz601887-dwarf4-rh-test.patch
      This adds a very simple test to check whether DWARF4
      is implemented. GDB has been using DWARF4 for several
      years, and the testsuite coverage supercedes this patch.
    - Remove gdb-6.6-buildid-locate-rpm-scl.patch
      This patch is applicable only on RHEL6 where .gdb_index
      version 5 is used. In recent GDBs, i.e., all DTS releases,
      this version could only be read with the option
      "use-deprecated-index-sections". RHEL7+ use .gdb_index version 8.
      Since RHEL6 is no longer supported, this is unnecessary.
      Also remove GDB_INDEX_VERIFY_VENDOR references/code from
      gdb-6.6-buildid-locate.patch and gdb.spec