tt: Fixup tt build for new includes locations

Some files were trying to access the global includes directy in the
build area with things like #include <api/c/tt_c.h>, which is now
wrong.  Se we fix all of those up.  tt_c.h and tttk.h are now global,
so we no longer need to root around various build dirs to find them.

TT builds again.

cde/lib/tt/slib/Makefile.am

@@ -4,12 +4,6 @@ include ../tooltalk.inc
 
 noinst_LIBRARIES = libstt.a
 
-BUILT_SOURCES = Tt
-CLEANFILES = Tt
-Tt: Makefile
-	$(RM) Tt
-	$(LN_S) ../lib/api/c Tt
-
 libstt_a_CXXFLAGS = $(TIRPCINC) $(TIRPC_DEFINES) -I../lib
 
 libstt_a_SOURCES = mp_ce_attrs.C mp_observer.C mp_observer_utils.C  \