allow/no_undefined_flag

[Roger While]

Problem applies from 1.x upto current stable 2.2.4.
allow_undefined_flag and no_undefined_flag are not being
expanded correctly at least under AIX (5.3). Probably other
architectures are affected as well.
This is the last part of a library link line from a make -
 -lc -Wl,-bnoentry  -qmaxmem=20000 -qarch=ppc -Wl,-bE:.libs/libgmp.exp 
${wl}-berok
Another example (last part of link line) -
-lc -Wl,-bnoentry  -Wl,-bexpfull -Wl,-bE:.libs/libcob.exp ${wl}-bernotok

Roger While