Here are some changes I want to make, I'll prepare some patch files
for you to look at hopefully soon enough:

* make gdb-mi support register filter in register buffer (the first patch)

* make gdb-mi support multiple memory display, so that I can monitor
  different memory locations at the same time

* make gdb-mi support expressions as memory location, e.g., $rsp, x+1.
  This mimics the display command of gdb, e.g. display/5gx $rsp.
  Currently, gdb-mi does supports expressions for setting memory
  monitors but translates it to a _fixed_ value; and the memory
  monitor doesn't reflect the chagne of the expression's value. For
  example, it does't follow $rsp and update address as $rsp chganges

* make gdb-mi support multiple gdb sessions at the same time.

Some questions:

* Is there any test that I can check my changes again to?

* Is the last one (multiple gdb sessions) neccessary? Have there been
  requests for it?