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Specifically, Platform_signals[] and Platform_numberOfSignals. Both are
not supposed to be mutable. Marking them 'const' puts them into rodata
sections in binary. And for Platform_numberOfSignals, this aids
optimization (aids only Link Time Optimization for now). :)
Signed-off-by: Kang-Che Sung <explorer09@gmail.com>

(Thanks @coypoop at #397 for the heads up!)

- currently implemented for darwin and linux

Closes #228.

Conflicts:
	Process.c
	Process.h
	ProcessList.c
	ScreenManager.c
	linux/LinuxProcessList.c

Set up environment to move other meters.