gdb.ada/maint_with_ada.exp: New testcase
    
    This commit adds a new testcase testing the "check-psymtabs" and
    "check-symtabs" maintenance commands.
    
    The "maintenance check-psymtabs" commands is currently known to
    produce some errors. While the situation was admetedly made worse
    by the following patch...
    
        commit b5ec771e60c1a0863e51eb491c85c674097e9e13
        Date:   Wed Nov 8 14:22:32 2017 +0000
        Subject: Introduce lookup_name_info and generalize Ada's FULL/WILD name matching
    
    ... hence the reference to PR gdb/22670, the command was already
    spotting one inconsistency prior to it:
    
        (gdb) maintenance check-psymtabs
        Global symbol `interfaces__cS' only found in /[...]/b~var_arr_typedef.adb psymtab
    
    For now, the "check-psymtab" test is KFAIL-ed.
    
    gdb/testsuite/ChangeLog:
    
            PR gdb/22670
            * gdb.ada/maint_with_ada: New testcase.
    
    Tested on x86_64-linux.