Add PMIX_QUERY_ABI_VERSION

 * Ref Issue #365
 * Add a `PMIX_QUERY_ABI_VERSION` attribute that can be passed to
   `PMIx_Query_info` to access the ABI version implementated by the
   associated PMIx library.

Signed-off-by: Joshua Hursey <jhursey@us.ibm.com>

Chap_API_Sync_Access.tex

@@ -771,6 +771,10 @@ \subsection{Query attributes}
 \declareAttributeNEW{PMIX_SERVER_INFO_ARRAY}{"pmix.srv.arr"}{pmix_data_array_t}{
 Array of \refstruct{pmix_info_t} about a given server, starting with its \refattr{PMIX_NSPACE} and including at least one of the rendezvous-required pieces of information.
 }
+%
+\declareAttributeNEW{PMIX_QUERY_ABI_VERSION}{"pmix.qry.abiversion"}{char *}{
+Query the \ac{ABI} version supported by the \ac{PMIx} library. The version returned will be of the form \code{"MAJOR.MINOR"}. For example. \code{"4.2"} representing version v4.2 of the \ac{PMIx} \ac{ABI}. NO QUALIFIERS.
+}
 
 \vspace{\baselineskip}
 These attributes are used to query memory available and used in the system.