IBMcxx complains that maxmem is as low as 2048 for certain modules

(like all the digests).  Setting maxmem to 16K seems to give the
compiler enough space to do all the optimization it wants.

Configure

@@ -305,7 +305,7 @@ my %table=(
 "unixware-7","cc:-O -DFILIO_H -Kalloca::-Kthread:-lsocket -lnsl:MD2_CHAR RC4_INDEX ${x86_gcc_des}::",
 
 # IBM's AIX.
-"aix-cc",   "cc:-O -DAIX -DB_ENDIAN::(unknown)::BN_LLONG RC4_CHAR:::",
+"aix-cc",   "cc:-O -DAIX -DB_ENDIAN -qmaxmem=16384::(unknown)::BN_LLONG RC4_CHAR:::",
 "aix-gcc",  "gcc:-O3 -DAIX -DB_ENDIAN::(unknown)::BN_LLONG RC4_CHAR:::",
 
 #