Philippe 29/04/2019: gamma_inc(_low): bug correction in argument check

(cherry picked from commit f234597f)

src/MNH/gamma_inc.f90

@@ -87,7 +87,7 @@ REAL                                 :: ZFPMIN=1.E-30
 REAL                                 :: ZAP,ZDEL,ZSUM
 REAL                                 :: ZAN,ZB,ZC,ZD,ZH
 !
-IF( PX<0.0 .OR. PA>=0.0 ) call Print_msg(NVERB_FATAL,'GEN','GAMMA_INC','invalid arguments: PX<0.0 .OR. PA>=0.0')
+IF( PX<0.0 .OR. PA<=0.0 ) call Print_msg(NVERB_FATAL,'GEN','GAMMA_INC','invalid arguments: PX<0.0 .OR. PA<=0.0')
 !
 IF( (PX.LT.PA+1.0) ) THEN
   ZAP = PA

src/MNH/gamma_inc_low.f90

@@ -109,7 +109,7 @@ ZS(5) = 2.9092306039
 !
 !*       1 Compute coefficients
 !
-IF( PX<0.0 .OR. PA>=0.0 ) call Print_msg(NVERB_FATAL,'GEN','GAMMA_INC_LOW','invalid arguments: PX<0.0 .OR. PA>=0.0')
+IF( PX<0.0 .OR. PA<=0.0 ) call Print_msg(NVERB_FATAL,'GEN','GAMMA_INC_LOW','invalid arguments: PX<0.0 .OR. PA<=0.0')
 !
 ZC(1) = 1.+ZP(1)*PA+ZP(2)*PA**2+ZP(3)*PA**3+ZP(4)*PA**4+ZP(5)*(EXP(-ZP(6)*PA)-1)
 !