Though in the last couple of discussions we agreed upon not trying to
push this idea into mainstream GDB, I am still uploading this patch as
I have found this useful for someone who tries to get some useful
patch-work done already but not readily available in the releases. I
beg pardon to people in this community. People in the community may
safely ignore this patch at their own will.

This patch implements a new gdb command namely, "plugin" to add and
delete custom gdb extensions at runtime. Plugins are shared libraries
supported by native OS.

Following new commands are added:

1. plugin (Without any argument this will list down existing GDB
plugins and with a plugin name as argument, will list down all new
commands introduced by the plugin)
2. plugin add <plugin> (Will add a plugin specified by a relative or
full path name of a shared library <plugin>. e.g. /usr/lib/gdb-ext.so)
3. plugin del <plugin> (Will delete an already added plugin specified
by a relative or full path name of a shared library <plugin>)

Plugin developer has to write his/her own plugin constructor and
destructor routine of a given prototype to export a set of commands
s/he wants to add in gdb command list. After adding a plugin the user
will be able to use the new set of commands introduced by the plugin
in gdb prompt.