Parse errors in the intermediate XML file now cause the backend to exit

Parse errors in the intermediate XML file now cause the backend to exit
immediately. The recovery infrastructure isn't there and segfaults are likely.

When no input is given to the backend program, it should not print an error
message, it should just return a non-zero exit status. The assumption is that
the frontend printed an error.

All backend error functions now use gblErrorCount.

git-svn-id: http://svn.complang.org/ragel/trunk@209 052ea7fc-9027-0410-9066-f65837a77df0