Add common functions to format and parse pathnames and numbers.

[stevenhl]

We need to come up with a decent naming convention for the .c file(s) and the function names themselves. Code of the form

      runemf2(SEPARATEKEEP | WINDOWED | MAXIMIZED,
	      hwnd, NULL, NULL, "%s %s%s%s", ad->info->test,
	      needs_quoting(ad->arcname) ? "\"" : NullStr,
	      ad->arcname,
	      needs_quoting(ad->arcname) ? "\"" : NullStr);

Is inefficient, hard to read and hard to maintain.

      runemf2(SEPARATEKEEP | WINDOWED | MAXIMIZED,
	      hwnd, NULL, NULL, "%s %s", ad->info->test,
	      quote_if_needed(ad->arcname));

is IMNSHO better. This is not as simple as it looks to implement. Any buffers allocated within the quoting function would need to be per thread. An simpler alternative add an additional argument and make the caller provide a work buffer

      runemf2(SEPARATEKEEP | WINDOWED | MAXIMIZED,
	      hwnd, NULL, NULL, "%s %s", ad->info->test,
	      quote_if_needed(ad->arcname, szBuf));

The buffer will only be used if quotes are needed. If quotes are not needed the function returns a pointer to the original string.