tgamma_spec() coverage

specification Unifloat *tgamma_spec( CallContext context, Unifloat *x, ErrorCode *errno )

coverages	branches	failures	hits/fails
C	X IS NORMAL POSITIVE		6
	X IS NEGATIVE	failure 23: Requirement failed: {tgammaf.05} If x is a negative integer a NaN shall be returned failure 24: Requirement failed: {tgamma.05} If x is a negative integer a NaN shall be returned failure 25: Requirement failed: {tgammal.05} If x is a negative integer a NaN shall be returned	3/3
	X IS ZERO		3
	X IS NAN		3
	X IS POSITIVE INFINITY		3
	X IS NEGATIVE INFINITY		3
	100% (6/6)		21/3