*) fix up buildexports.sh:

   - enable it to be run from any dir by passing a parameter for the
     location of srclib, and using its own location for determining where
     the AWK script is located
   - accept exports files on STDIN, and produce output on STDOUT
   - use "pwd" and cd back to it, rather than assuming ../../.. (which might
     not apply if we feed it other export files)
   - add USAGE reporting

*) generate exports.c during normal build of "server" rather than during the
   buildconf stage. update invocation to match above changes

*) revamp the ap_ugly_hack referencing in main.c: put it at the bottom of
   the file with the other, similar references, and style it similarly.

*) remove the ap_ugly_hack declaration from http_main.h; it is internal to
   the "server" code


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@87249 13f79535-47bb-0310-9956-ffa450edef68