exports.c was dependent upon delete-exports, but that dependency will always

exports.c was dependent upon delete-exports, but that dependency will always
fail since there is no delete-exports file (thus, exports.c would always get
regenerated, recompiled, and relinked). Instead, we move the delete-exports
target "up" to the "all" target. However, ltlib.mk doesn't allow us to add
things to the "all" target, so we also revise the set of .mk files to use.

also use TARGET_EXPORTS consistently.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@87449 13f79535-47bb-0310-9956-ffa450edef68