Set defines for Doxygen

OTCrypto_OpenSSL and Lucre stuff was missing from the Doxygen docs.

Maybe not the best way to pass defines one-by-one but my CMake skills are
lacking here.

cmake/Doxyfile.in

@@ -1942,7 +1942,7 @@ INCLUDE_FILE_PATTERNS  =
 # recursively expanded use the := operator instead of the = operator.
 # This tag requires that the tag ENABLE_PREPROCESSING is set to YES.
 
-PREDEFINED             =
+PREDEFINED             = OT_CRYPTO_USING_OPENSSL OT_CASH_USING_LUCRE
 
 # If the MACRO_EXPANSION and EXPAND_ONLY_PREDEF tags are set to YES then this
 # tag can be used to specify a list of macro names that should be expanded. The