Request for additional installbuilddir exports

[Jacob Champion]

Hi all,

Sorry for the post-1.6 timing on this. Over at httpd I'm trying to 
engineer a build that doesn't require checking out APR and friends, but 
only depends on files that are part of the APR installation.

httpd depends on apr_common.m4, find_apr.m4, and find_apu.m4. On 
Debian-derived distros, those files are part of the libapr-dev packaging 
-- but as far as I can tell, they're not included in the official 
builds, so my solution isn't portable. Any chance we could get those 
three (plus any other build-time helpers you think downstream projects 
may need to use) added to the official installbuilddir?

--Jacob