checking for non-standard headers

[Larry Siden]

How can I get autoconf to automatically find header files that are not
part of the standard include path, but for which *.pc files exist?

I want to check for non-standard headers, such as, pango/pango.h,
glib.h, and others.  AC_CHECK_HEADER seems to work only for standard
headers, i.e. headers that can be found in the standard include path. 
How can I augment the include path for other headers?  

I am calling "PKG_CHECK_MODULES(MODULES, pango glib-2.0)" to set
MODULES_CFLAGS, but don't know how to append this info to the include
path used by autoconf.

configure.ac
Description: Text document