Tidy up mdoc formatting for "etc.)" at end of line

man(1) has some logic to use two spaces after a full stop, which is
useful for spotting sentence breaks in monospace fonts.  However,
this logic is very simple, treating almost all '.' characters as
end-of-sentence markers, unless followed by certain other
characters.  For example, '.,' is not end-of-sentence, and neither
is ".) ", but ".)" at the end of a line triggers the sentence-end
detection.

Apply a zero-width space to a few instances of this in share/man,
and also supply a missing full stop for an instance that occurred at
the end of a sentence.

Leave untouched several instances that are at the end of a sentence
or list element.

Reported by:	0mp (ieee80211.9)

share/man/man5/stab.5

@@ -42,7 +42,7 @@ The file
 defines some of the symbol table
 .Fa n_type
 field values for a.out files.
-These are the types for permanent symbols (i.e., not local labels, etc.)
+These are the types for permanent symbols (i.e., not local labels, etc.\&)
 used by the old debugger
 .Em sdb
 and the Berkeley Pascal compiler

share/man/man9/ieee80211.9

@@ -59,7 +59,7 @@ device driver implements a virtual radio API that is exported to
 users through network interfaces (aka vaps) that are cloned from the
 underlying device.
 These interfaces have an operating mode
-(station, adhoc, hostap, wds, monitor, etc.)
+(station, adhoc, hostap, wds, monitor, etc.\&)
 that is fixed for the lifetime of the interface.
 Devices that can support multiple concurrent interfaces allow
 multiple vaps to be cloned.

share/man/man9/ieee80211_vap.9

@@ -62,7 +62,7 @@ a virtual radio API that is exported to
 users through network interfaces (aka vaps) that are cloned from the
 underlying device.
 These interfaces have an operating mode
-(station, adhoc, hostap, wds, monitor, etc.)
+(station, adhoc, hostap, wds, monitor, etc.\&)
 that is fixed for the lifetime of the interface.
 Devices that can support multiple concurrent interfaces allow
 multiple vaps to be cloned.

share/man/man9/taskqueue.9

@@ -404,7 +404,7 @@ the
 .Va init
 argument to the macro is executed as a C statement,
 allowing any further initialisation to be performed
-(such as registering an interrupt handler etc.)
+(such as registering an interrupt handler, etc.).
 .Pp
 The
 .Fn TASKQUEUE_DEFINE_THREAD

share/man/man9/vnode.9

@@ -82,7 +82,7 @@ system calls.
 Any call which returns a vnode (e.g.,\&
 .Xr vget 9 ,
 .Xr VOP_LOOKUP 9 ,
-etc.)
+etc.\&)
 will increase the
 .Va v_usecount
 of the vnode by one.