Support -j on SyncTERM

This doesn't make anything much faster since the bulk of the time
is building ctyptlib which doesn't support -j, but at least Cyan
won't complain every time he creates an ebuild anymore.

src/syncterm/GNUmakefile

 SRC_ROOT	:=	..
 include ${SRC_ROOT}/build/Common.gmake
+include extdeps.mk
 
 ifdef WITHOUT_OOII
  CFLAGS	+= -DWITHOUT_OOII=1

src/syncterm/extdeps.mk

+$(MTOBJODIR)$(DIRSEP)syncterm$(OFILE): $(CRYPT_LIB)
+$(MTOBJODIR)$(DIRSEP)st_crypt$(OFILE): $(CRYPT_LIB)
+$(MTOBJODIR)$(DIRSEP)ssh$(OFILE): $(CRYPT_LIB)