Improve dbt with stackframe contents

[radare]

We want to show the contents of the stackframe, maybe via pxr or ad if we dont have local vars defined for the given function

$ r2 -d rax2
[0x100004000]> dcu entry0
Continue until 0x100000f60 using 1 bpsize
[0x10004428e]> dbt
0  0x100048642        sp: 0x0                 0    [??]  rip map.rax2.r+288322
1  0x10000e452        sp: 0x7ffeefbfe3e8      16   [??]  map.rax2.r+50258
2  0x100040dc0        sp: 0x7ffeefbfe468      128  [??]  map.rax2.r+257472
3  0x10000e452        sp: 0x7ffeefbfe4f8      144  [??]  map.rax2.r+50258
4  0x1000084b9        sp: 0x7ffeefbfe538      64   [??]  map.rax2.r+25785
5  0x100007ff5        sp: 0x7ffeefbfe728      496  [??]  map.rax2.r+24565
[0x10004428e]>