[liba] Implement isnan and isinf as specified by the C99 standard

Change-Id: Ie767503568b7391d421a46052a1fc4a85b4006c7

liba/include/math.h

@@ -5,8 +5,16 @@
 
 LIBA_BEGIN_DECLS
 
+/* The C99 standard requires isinf and isnan to be defined as macros that can
+ * handle arbitrary precision float numbers. The names of the functions called
+ * by those macros (depending on the argument size) are not standardized though.
+ * We're chosing isinff/isnanf for single-precision functions (which is the only
+ * case we're actually handling). */
+
 int isinff(float x);
+#define isinf(x) isinff(x)
 int isnanf(float x);
+#define isnan(x) isnanf(x)
 
 float copysignf(float x, float y);
 float cosf(float x);