Fix rounding issues with sqrt/sqrtf

- compiler is sometimes optimizing out the rounding check in
  e_sqrt.c and ef_sqrt.c which uses two constants to create
  an inexact operation
- there is a similar constant operation in s_tanh.c/sf_tanh.c
- make the one and tiny constants volatile to stop this

newlib/libm/math/e_sqrt.c

@@ -86,9 +86,9 @@
 #ifndef _DOUBLE_IS_32BITS
 
 #ifdef __STDC__
-static	const double	one	= 1.0, tiny=1.0e-300;
+static	const volatile double	one	= 1.0, tiny=1.0e-300;
 #else
-static	double	one	= 1.0, tiny=1.0e-300;
+static	double	volatile one	= 1.0, tiny=1.0e-300;
 #endif
 
 #ifdef __STDC__

newlib/libm/math/ef_sqrt.c

@@ -16,9 +16,9 @@
 #include "fdlibm.h"
 
 #ifdef __STDC__
-static	const float	one	= 1.0, tiny=1.0e-30;
+static	const volatile float	one	= 1.0, tiny=1.0e-30;
 #else
-static	float	one	= 1.0, tiny=1.0e-30;
+static	float	volatile one	= 1.0, tiny=1.0e-30;
 #endif
 
 #ifdef __STDC__

newlib/libm/math/s_tanh.c

@@ -73,9 +73,9 @@ PORTABILITY
 #ifndef _DOUBLE_IS_32BITS
 
 #ifdef __STDC__
-static const double one=1.0, two=2.0, tiny = 1.0e-300;
+static const volatile double one=1.0, two=2.0, tiny = 1.0e-300;
 #else
-static double one=1.0, two=2.0, tiny = 1.0e-300;
+static double volatile one=1.0, two=2.0, tiny = 1.0e-300;
 #endif
 
 #ifdef __STDC__

newlib/libm/math/sf_tanh.c

@@ -16,9 +16,9 @@
 #include "fdlibm.h"
 
 #ifdef __STDC__
-static const float one=1.0, two=2.0, tiny = 1.0e-30;
+static const volatile float one=1.0, two=2.0, tiny = 1.0e-30;
 #else
-static float one=1.0, two=2.0, tiny = 1.0e-30;
+static volatile float one=1.0, two=2.0, tiny = 1.0e-30;
 #endif
 
 #ifdef __STDC__