Add comments describing valid argument range for internal functions

src/e_j0.c

@@ -268,6 +268,7 @@ static const double pS2[5] = {
   1.46576176948256193810e+01, /* 0x402D50B3, 0x44391809 */
 };
 
+	/* Note: This function is only called for ix>=0x40000000 (see above) */
 	static double pzero(double x)
 {
 	const double *p,*q;
@@ -363,6 +364,7 @@ static const double qS2[6] = {
  -5.31095493882666946917e+00, /* 0xC0153E6A, 0xF8B32931 */
 };
 
+	/* Note: This function is only called for ix>=0x40000000 (see above) */
 	static double qzero(double x)
 {
 	const double *p,*q;

src/e_j0f.c

@@ -224,6 +224,7 @@ static const float pS2[5] = {
   1.4657617569e+01, /* 0x416a859a */
 };
 
+	/* Note: This function is only called for ix>=0x40000000 (see above) */
 	static float pzerof(float x)
 {
 	const float *p,*q;
@@ -319,6 +320,7 @@ static const float qS2[6] = {
  -5.3109550476e+00, /* 0xc0a9f358 */
 };
 
+	/* Note: This function is only called for ix>=0x40000000 (see above) */
 	static float qzerof(float x)
 {
 	const float *p,*q;

src/e_j1.c

@@ -262,6 +262,7 @@ static const double ps2[5] = {
   8.36463893371618283368e+00, /* 0x4020BAB1, 0xF44E5192 */
 };
 
+	/* Note: This function is only called for ix>=0x40000000 (see above) */
 	static double pone(double x)
 {
 	const double *p,*q;
@@ -358,6 +359,7 @@ static const double qs2[6] = {
  -4.95949898822628210127e+00, /* 0xC013D686, 0xE71BE86B */
 };
 
+	/* Note: This function is only called for ix>=0x40000000 (see above) */
 	static double qone(double x)
 {
 	const double *p,*q;

src/e_j1f.c

@@ -219,6 +219,7 @@ static const float ps2[5] = {
   8.3646392822e+00, /* 0x4105d590 */
 };
 
+	/* Note: This function is only called for ix>=0x40000000 (see above) */
 	static float ponef(float x)
 {
 	const float *p,*q;
@@ -315,6 +316,7 @@ static const float qs2[6] = {
  -4.9594988823e+00, /* 0xc09eb437 */
 };
 
+	/* Note: This function is only called for ix>=0x40000000 (see above) */
 	static float qonef(float x)
 {
 	const float *p,*q;