top: attempt to provide missing xterm vim keys support

A recent issue (and merge request) reminded me of gaps
in top's alternate 'vim' navigation keys support. Some
xterm emulators do not pass the customary strings when
keys were used with the <Ctrl> and/or <Alt> modifiers.

While it was a known problem, this issue/merge request
prompted research into the root cause. As it turns out
the problem is traceable to an X resource known by the
name 'eightBitInput'. When 'true' (the default), a key
pressed in combination with <Alt> will not be preceded
by the <Esc> character. Rather, a single character was
presented (modified via an 'eightBitMeta' X resource).

The following approaches would eliminate this problem:

. start xterm thus: xterm -xrm '*eightBitInput: false'

. use: ~/.Xresources with 'Xterm*eightBitInput: false'

. build xterm with 'configure --enable-meta-sends-esc'
( apparently used for CentOS, Fedora, openSUSE, etc. )

. enable xterm's menu via 'configure --enable-toolbar'
( so the user can set the 'Meta Sends Escape' option )

Of course, none of the above steps is desirable from a
user's perspective. So, this patch will add additional
entries to the iokey function's tinfo_tab to represent
strings passed when the <Alt> key does not send <Esc>.

[ hopefully they'll be the same across all platforms ]

Lastly, this patch will also eliminate those redundant
<Atl> + '\', '/', '<' & '>' provisions, which now seem
like overkill and suffer from that same 'eightBitMeta'
xterm problem. And we might as well say goodbye to the
4 '<Alt> + arrow key' table entries (which do not seem
to currently work with any emulator which I can find).

[ what in the world was I thinking way back in 2011? ]

Reference(s):
. issue
https://gitlab.com/procps-ng/procps/issues/135
. merge request
https://gitlab.com/procps-ng/procps/merge_requests/84

Signed-off-by: Jim Warner <james.warner@comcast.net>

NEWS

@@ -8,6 +8,7 @@ procps-ng-NEXT
   * top: preserves 'other filters' in configuration file   issue #99
   * top: can now collapse/expand forest view children      issue #99
   * top: parent %CPU time includes collapsed children
+  * top: improve xterm support for vim navigation keys     issue #135
 
 procps-ng-3.3.15
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