Use more flexible command substitution for shared library generation, so we can

Use more flexible command substitution for shared library generation, so we can
dump makeshlib.sh.  Use the new saved export list files for AIX.

* aclocal.m4 (KRB5_BUILD_LIBRARY_WITH_DEPS): Substitute MAKE_SHLIB_COMMAND, not
LDCOMBINE and LDCOMBINE_TAIL.
* pre.in (DO_MAKE_SHLIB, SHLIB_STATIC_TARGET, LDCOMBINE, LDCOMBINE_TAIL):
Delete unused variables.
(SHLIB_EXPORT_FILE, SHLIB_EXPORT_FILE_DEP, MAKE_SHLIB_COMMAND): New variables.
* config/lib.in (lib$(LIB)$(SHLIBVEXT)): Set objlist to the list of object
files before invoking MAKE_SHLIB_COMMAND, instead of wrapping the list with
LDCOMBINE and LDCOMBINE_TAIL.  Depend on SHLIB_EXPORT_FILE_DEP.
* config/shlib.conf: Set MAKE_SHLIB_COMMAND, using LDCOMBINE and LDCOMBINE_TAIL
in the common case.
(case *-*-aix*): Specify new commands, taken from makeshlib.sh,	but assume the
export list is provided externally.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@16263 dc483132-0cff-0310-8789-dd5450dbe970