Use new-style variable expansion for light.exe

With WiX 3.x, the preprocessor candle.exe expands variables using
$(); the linker light.exe expands localization and similar variables
using !(), though it accepts the $() form and prints a warning.

Switch to using the expected form to silence the warnings.

ticket: 7390
tags: pullup
target_version 1.11.4
Remove OldCC/rpc.cxx

It is only linked on one place, which does not use any of the
exported routines, since an alternate implementation is linked first.

Remove the dead code and reduce the number of warnings omitted by
the build process.
Use better URL for kerberos documentation

We have added a krb5-latest symlink for the latest stable release,
which is preferred to the krb5-current link (which points to a nightly
build of master).

ticket: 7673 (new)
ticket: 7493
queue: kfw
tags: pullup
target_version: 1.11.4
Be smarter about installing debug symbols

We know when we're going to generate debug symbols, so only attempt
to install them when we know they should be present.

This eliminates the need to tell make to ignore errors from the shell
on these steps.

ticket: 7317
tags: pullup
target_version: 1.11.4