Makefile.am: Specify hoxsl-generated apply stylesheets

This will speed up compilation a bit.

* Makefile.am (apply_src): Manually specify apply files.

Makefile.am

@@ -23,9 +23,8 @@ path_test = test
 path_aux  = build-aux
 
 # all source files will be run through hoxsl; see `applies' target
-apply_src  := $(shell find "$(path_src)" "$(path_test)" \
-                        -name '*.xsl' \
-                        -a \! -path "$(path_src)"/current/\* )
+apply_src := $(path_src)/graph.xsl $(path_src)/symtable.xsl \
+             $(path_src)/symtable/symbols.xsl $(path_test)/graph-test.xsl
 apply_dest := $(apply_src:%.xsl=%.xsl.apply)
 
 # needed by test runner