rc3 was accidentally posted on the web site for a short while, so just
be safe and bump to rc4.

It looks like we didn't update the shared library versions since
v1.6. :-(

Here's what the values were for 1.6:

{{{
libmpi_so_version=1:3:0
libmpi_cxx_so_version=1:1:0
libmpi_f77_so_version=1:3:0
libmpi_f90_so_version=2:0:1
libopen_rte_so_version=4:0:0
libopen_pal_so_version=4:0:0
libmca_common_sm_so_version=3:0:0
libmca_common_mx_so_version=1:0:0
libmca_common_portals_so_version=1:0:0
}}}

Here's what we ''should'' have changed the values to for v1.6.1:

{{{
libmpi_so_version=1:4:0 -- changed
libmpi_cxx_so_version=1:1:0
libmpi_f77_so_version=1:4:0 -- changed
libmpi_f90_so_version=3:0:0 -- changed; interface changed
libopen_rte_so_version=4:1:0 -- changed
libopen_pal_so_version=4:1:0 -- changed
libmca_common_sm_so_version=3:0:0
libmca_common_mx_so_version=1:1:0 -- changed
libmca_common_portals_so_version=1:0:0
}}}

And here's what we ''should'' have changes the values to for v1.6.2:

{{{
libmpi_so_version=1:5:0 --changed
libmpi_cxx_so_version=1:1:0
libmpi_f77_so_version=1:5:0 --changed
libmpi_f90_so_version=3:0:0
libopen_rte_so_version=4:2:0 --changed
libopen_pal_so_version=4:2:0 --changed
libmca_common_sm_so_version=3:0:0
libmca_common_mx_so_version=1:1:0
libmca_common_portals_so_version=1:0:0
}}}

Based on those changes, this commit represents the values that we
would have used if we had actually made the proper changes for 1.6.1
and 1.6.2:

{{{
libmpi_so_version=1:6:0 --changed
libmpi_cxx_so_version=1:1:0
libmpi_f77_so_version=1:6:0 --changed
libmpi_f90_so_version=4:0:1 --changed; added new interfaces
libopen_rte_so_version=4:3:0 --changed
libopen_pal_so_version=4:3:0 --changed
libmca_common_sm_so_version=3:0:0
libmca_common_mx_so_version=1:1:0
libmca_common_portals_so_version=1:0:0
}}}

Update NEWS file for 1.6.3.

Add 1.6.3 bullets

Fixes #3360: Fix launch-agent behavior to avoid prefix being added

Custom patch from ticket.

1.7rc2 has been released; on to 1.7rc3

1.7rc1 has already been released; on to 1.7rc2

Fix visibility so --with-hwloc will build

Make --without-hwloc build/work again using r27377 plus some hand edits

Fix backwards asserts in the OPAL hotel code.