Add SDL_FLT_EPSILON.

include/SDL_stdinc.h

@@ -234,6 +234,19 @@ typedef uint64_t Uint64;
 
 /* @} *//* Basic data types */
 
+/**
+ *  \name Floating-point constants
+ */
+/* @{ */
+
+#ifdef FLT_EPSILON
+#define SDL_FLT_EPSILON FLT_EPSILON
+#else
+#define SDL_FLT_EPSILON 1.1920928955078125e-07F /* 0x0.000002p0 */
+#endif
+
+/* @} *//* Floating-point constants */
+
 /* Make sure we have macros for printing width-based integers.
  * <stdint.h> should define these but this is not true all platforms.
  * (for example win32) */