That lets the version of Wireshark built with autotools find the extcap
programs.
Don't install the extcap programs under ${datadir} - that puts it under
a share directory, and share directories are for platform-independent
files, which executable images aren't (they're instruction-set
dependent, hence platform-dependent).
Change-Id: I992eeb984bdbe6b3476777f7114628c83df6080f
Reviewed-on: https://code.wireshark.org/review/13943
Reviewed-by: Guy Harris <guy@alum.mit.edu>
Guy Harris