WL#2072: Extract more complete information for 'help'

We have a way of getting "help" information from the manual 
(manual.texi) into a help database, so that a client program 
like mysql can support user help requests on topics that are 
documented. The main mechanism for this is a script that 
searches for markup in manual.texi that indicates an example 
is beginning/ending. One problem, reported in BUG#4862, was 
that the script found only the first marked-up area -- if 
there was any intervening text, it wasn't copied to the help 
database, and so the support information appeared incomplete. 
 
Since the documentation henceforth will be in DocBook (not .texi) 
format, some revision is necessary in any case.  
 
This task is in the client raw idea bin, because the original task 
(WL#16) was there. But it might be reassignable: to the doc team 
because because they know where other Perl scripts for DocBook are, 
or to the GUI team since they too have a "help" option.  
 
See also: 
WL#16 "Command line help for MySQL" client-sprint task (done) (Jani). 
BUG#4862 'help' topics sometimes contain only one syntax ... (Harrison).