Replace Makefile.in dependencies on expr.h with variable $(EXPR_H),

Replace Makefile.in dependencies on expr.h with variable $(EXPR_H),

which contains headers also pulled in via expr.h.
        * Makefile.in (EXPR_H): New dependency variable.
        (c-typeck.o): Depend on $(EXPR_H) instead of expr.h.
        (c-iterate.o): Likewise.
        (gencheck): Depend on $(TREE_H) instead of tree.h, etc.
        (stor-layout.o): Depend on $(EXPR_H) instead of expr.h.
        (toplev.o): Likewise.  Also depend on $(RECOG_H) instead of recog.h.
        (varasm.o): Depend on $(EXPR_H) instead of expr.h.
        (function.o): Likewise.
        (stmt.o): Likewise.
        (except.o): Likewise.
        (expr.o): Likewise.
        (calls.o): Likewise.
        (expmed.o): Likewise.
        (explow.o): Likewise.
        (optabs.o): Likewise.
        (sdbout.o): Likewise.
        (dwarf2out.o): Likewise.
        (emit-rtl.o): Likewise.
        (integrate.o): Likewise.
        (jump.o): Likewise.
        (cse.o): Likewise.
        (gcse.o): Likewise.  Also depend on $(BASIC_BLOCK_H) instead of
        basic-block.h.
        (loop.o): Depend on $(EXPR_H) instead of expr.h.
        (unroll.o): Likewise.
        (combine.o): Likewise.
        (reload.o): Likewise.
        (reload1.o): Likewise.
        (caller-save.o): Likewise.
        (reorg.o): Likewise.
        (alias.o): Don't depend on insn-codes.h.
        (regmove.o): Depend on $(RECOG_H)/$(EXPR_H) instead of recog.h/expr.h.
        (insn-emit.o): Depend on $(EXPR_H) instead of expr.h.
        (insn-opinit.o): Likewise.

From-SVN: r20748