This is apr version 0.9.2. I'd downloaded `subversion' (version 0.20.1, if it matters), which includes a copy of apr. I didn't have the `crypt' package installed, because I didn't know that I needed it. `configure' failed like the Subject line says. Once I installed the `crypt' package, everything worked fine.
I suspect the problem is that, on Cygwin, build/apr_hints.m4 unconditionally adds `-lcrypt' to LIBS; since I didn't have that library, its test for the presence of `mmap' and `munmap' failed at link time, and `configure' incorrectly assumed that the reason for the failure was the lack of those functions. (In fact, the reason was the lack of the `crypt' library.) It's not clear that the `crypt' library is necessary. If it isn't necessary, then of course the fix is to remove the APR_ADDTO. But if it is, then ideally configure should die with a message to the effect of "-lcrypt is required". -- People studying literature rarely say anything that would be of the slightest use to those producing it. -- Paul Graham