assume that runes are format (but not flags).  this allows
a format of Γ to yield this warning:

	8c -FTVw vmx.c
	warning: vmx.c:2845 format mismatch 13Γ VLONG, arg 4

rather than the somewhat obtuse

	warning: vmx.c:2845 format mismatch 13 VLONG, arg 4

for the format "%13Γ".