Not so much a solution, but after wasting all night on this I do at least have a work-around. Had the same issue myself - mod_mono doesn't compile against Apache 2.2.2 - it seems the apache version checking routine invoked when running mod_mono's ./configure fails to compile now resulting in the erroneous reporting of version 1.3:
configure:20643: checking Apache version
configure:20665: gcc -c -g -O2 -I/usr/local/httpd/apache-2.2.2/include conftest.c >&5
In file included from /usr/local/httpd/apache-2.2.2/include/apr_general.h:28,
/usr/local/httpd/apache-2.2.2/include/apr.h:270: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'apr_off_t'
configure:20671: $? = 1
Didn't have the skills to fix that, so I just forced the selection of Apache 2.2 by editing the file "configure" inside the mod_mono source directory. You'll find a couple of lines that say:
Change those lines to 2.2 and ./configure sets the build up for a successful compile.
Hope this helps.