Turns out that AC_CHECK_DECLS is one of the "new style" Autoconf
macros that #defines the output to be 0 or 1 (vs. #define'ing or
#undef'ing it). So don't check for "#if defined(..."; just check for
"#if ...".
This commit was SVN r29059.
The following Trac tickets were found above:
Ticket 3730 --> https://svn.open-mpi.org/trac/ompi/ticket/3730