debugger tests failing due to problem with MR_edt_root_node

[Fergus Henderson]

Hi,

The debugger tests are failing in all grades on murlibobo (and probably
elsewhere too).
The problem seems to be that the symbol MR_edt_root_node is undefined.
The linker gives a warning that this symbol is undefined when building
libmer_browser.so, and then when you build executables linked to that
library the dynamic loader reports an error at runtime.
It looks very much like this is due to some problem with Mark Brown's
recent change.  Mark, could you please have a look at this one?

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>  |  of excellence is a lethal habit"
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