[Gpsbabel-code] Yet Another Google Fix

[Ron P. <ro...@pa...>]

I got mail off-list from someone whose Google Maps instructions included 
the nbsp entity, which our google reader was puking on.  Yesterday, I 
checked in a temporary fix that just replaced " " with a space 
(it's really a non-breaking space, 0xA0, but for our application, it 
didn't matter much.)  It was a temporary fix because, obviously, there 
could be a lot of other entities that cause the same problem.

The current CVS version now contains a new module, xhtmlent.c, that 
declares a global string containing all of the entity declarations for 
XHTML 1.0.  I also added a new function, xml_readprefixstring, to 
xmlgeneric.  This function will read a constant string but not terminate 
the parser, so that you can concatenate multiple strings together by 
calling xml_readprefixstring for all but the last.  This allows me to 
feed the parser a synthetic doctype declaration - including all of the 
entity declarations I just added - for the XHTML snippet that we extract 
from Google Maps data.  That, in turn, lets expat do all of the 
entity-substitution heavy lifting, which I assume it's somewhat 
optimized for.

The point of all this is to say that if you need to parse XHTML data, or 
if you need to parse any data that may contain undefined parsed entities 
(http://www.w3.org/TR/2006/REC-xml-20060816/#sec-physical-struct) for 
which you need to include a DTD, you can find code to do that in the new 
google.c.

While I was at it, I rewrote the part of the code that cleans up the 
extracted XHTML to get it into a parseable format, making it closer to 
O(n) than to O(n*m).  (In my checkin comments, I said O(n^2), but it was 
really O(n*m) where n is the length of the string and m is the number of 
substitutions that have to be made.)