[MAT-431] Rename real16->real8

In the root dir:

`find . -type f -print0 | xargs -0 sed -i 's/Real16/Real8/g'`
`find . -type f -print0 | xargs -0 sed -i 's/real16/real8/g'`

And fix up the symbol name for the OS X backtrace test in
check_exceptions.cc because the method name is now 20 chars.
(Many thanks to Stuart A for spotting that one!)
[MAT-431] Use types consistently in jdispatch

Rename double -> real8
Rename complex<double> -> complex16
[MAT-431] Use real8 consistently vs. double

In src/librdag:

`find . -type f -print0 | xargs -0 sed -i 's/double/real8/g'`