Find Tcl includes

Index: src/Makefile.in
--- src/Makefile.in.orig
+++ src/Makefile.in
@@ -397,7 +397,7 @@ AM_CPPFLAGS = ${TCL_INCLUDE_SPEC} -DELTCLSH_DATA='"${d
 	-DELTCLSH_VERSION='"${PACKAGE_VERSION}"'
 eltclsh_LDFLAGS = ${RUNTIME_PATH}
 eltclsh_LDADD = libcommon.la ${TCL_LIB_SPEC}
-elwish_CPPFLAGS = ${TK_INCLUDE_SPEC} ${TK_XINCLUDES}
+elwish_CPPFLAGS = ${TK_INCLUDE_SPEC} ${TK_XINCLUDES} ${TCL_INCLUDE_SPEC}
 elwish_LDFLAGS = ${RUNTIME_PATH}
 elwish_LDADD = libcommon.la ${TK_LIB_SPEC} ${TCL_LIB_SPEC}