GDB round 2

[John Baldwin]

I am testing a patch that follows a compromise suggested by kib at .
The patch adds a new make knob WITH_GDB_LIBEXEC which installs 'gdb' and
'kgdb' to /usr/libexec instead of /usr/bin for use by crashinfo.  It then
alters the defaults so that GDB now installs to /usr/libexec on the
platforms where it was previously disabled entirely.

The patch is posted for review at https://reviews.freebsd.org/D10449

-- 
John Baldwin