[BRLTTY] Debugging support

[Yannick PLASSIARD]

Hi all:
	While compiling brltty , I noticed that the -g flag was passed, overloading the -O2 flag. Would it be good to increase speed and significantly reduce the executable and libraries' sizes, to make an option "--enable-debug" which would add the -g flag if defined, or just add a -O2 flag if not ?
	Of cours I think that duing a "strip" on binaries and libs could lead tu the same sizes but 'regular users' don't necessarilly know the strip command and its usage .

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	Yannick PLASSIARD