Add dependencies to fix loaddefs race during parallel builds.

Add dependencies to fix loaddefs race during parallel builds.

Without this, for example, 'make -j bootstrap' can fail and report
"Opening input file: no such file or directory,
.../lisp/calendar/diary-loaddefs.el ... recipe for target
'calendar/hol-loaddefs.el' failed", where the hol-loaddefs.el rule
got confused because diary-loaddefs.el was being built in parallel.
* Makefile.in ($(CAL_DIR)/diary-loaddefs.el):
Depend on $(CAL_DIR)/cal-loaddefs.el.
($(CAL_DIR)/hol-loaddefs.el): Depend on $(CAL_DIR)/diary-loaddefs.el.