Begin refactor of libm-test.inc

Attempt to creatively redefine the macros
to choose tests based on the format being
tested, not the type.

Note, TS 18661 does not define any printf
modifiers, so we need to be a little more
verbose about constructing strings to
output.

math/test-double.h

@@ -23,3 +23,7 @@
 #define PRINTF_NEXPR "f"
 #define TEST_DOUBLE 1
 #define BUILD_COMPLEX(real, imag) (CMPLX ((real), (imag)))
+#define PREFIX DBL
+#define LIT(x) (x)
+#define TYPE_STR "double"
+#define FTOSTR snprintf