Append '-no_fixup_chains' flag to disable chained fixups since it
is not compatible with '-undefined dynamic_lookup'.
* m4/libtool.m4: AC_VAR_APPEND will handle appending the option to
the variable, which allows the '+=' extension to be used by shells
that provide this capability for more efficient scaling. Also, bump
minimum required version of autoconf from 2.62 to 2.64.
* tests/no-executables.at: Set cache variable for link test.
* NO-THANKS: Add thanks for Carlo Cabrera and Dave Allured.