Yaesu newcat style command response reading improvements

After testing on an FT-450D which tends to send busy responses "?;" to
subsequent commands after a band  changing command it appears that the
undoumented "?;"  rig busy response  should be  treated as a  wait and
subsequent reads may return the  expected response i.e. the command is
still in progress and should not be resent.

As this is  all based on observations of failure  modes rater than any
doumentation from Yaesu, there may be further enhancements necessary.
Increase communications timeout for Icom rigs

Icom  users, who  use  the  K9JM CI-V  router  to  protect their  PW-1
amplifiers from  damage due to  Icom's broken CI-V  protocol handling,
require a 1s delay  after opening the serial port. This  is due to the
router  using  an  Arduino  &  Arduino  USB  adapter  that  employs  a
bootloader which  holds the RS-232  interface for 1s after  reset (DTR
releases reset).   Hamlib already  has a  retry and  timeout mechanism
which was  set to 3 and  200ms respectively for most  Icom rigs.  This
change increses that  timeout to 1s. The increaased  timeout will have
little or no impact on clients as  it only comes into play if there is
a problem.
Revert read_string() to partial results are a success status

The read_string() function was changed to return a -RIG_ETIMEOUT error
when timing out after having read  some characters. This caused a back
end to fail because it was  using a read_string() with an invalid stop
character  and relying  on the  timed out  read_string() to  fetch the
data. This  patch reverts to  the prior  behavior of returning  a null
terminated buffer and  read bytes count if at least  one byte has been
read.
Remove gratuitous sleeps before function exits

Add sleep in tight wait loop to reduce CPU loading.
Merge branch 'yaesu-busy' of git://git.code.sf.net/u/bsomervi/hamlib
Merge branch 'icom-longer-timeout' of git://git.code.sf.net/u/bsomervi/hamlib
TenTec Omni VII update from W9MDB

Implement all current TenTec Omni VII commands.