tests for some ifdef errors
makefile preprocessor! started as a test for the vline iterator in pymake but is now a make preprocessor
add line numbers to preprocessed output
refactor some code into general purpose makefile preprocessor (joins backslashed lines, strips blank lines and comment lines);  sloppy start to handling directives;
add some tests to verify make ignores false conditional blocks; add if/else/else/else test
add slightly ridiculous macro to search for a program in $PATH