Apply all source related changes for the new INSTALL.md in one commit.

For people who want to have dkPless builds in their repo.

tools/preproc/Makefile

@@ -8,12 +8,18 @@ SRCS := asm_file.cpp c_file.cpp charmap.cpp preproc.cpp string_parser.cpp \
 HEADERS := asm_file.h c_file.h char_util.h charmap.h preproc.h string_parser.h \
 	utf8.h
 
+ifeq ($(OS),Windows_NT)
+EXE := .exe
+else
+EXE :=
+endif
+
 .PHONY: all clean
 
-all: preproc
+all: preproc$(EXE)
 	@:
 
-preproc: $(SRCS) $(HEADERS)
+preproc$(EXE): $(SRCS) $(HEADERS)
 	$(CXX) $(CXXFLAGS) $(SRCS) -o $@ $(LDFLAGS)
 
 clean: