patch 9.0.0491: no good reason to build without the float feature

Problem:    No good reason to build without the float feature.
Solution:   Remove configure check for float and "#ifdef FEAT_FLOAT".
diff --git a/src/macros.h b/src/macros.h
index aa61d90..16aab2e 100644
--- a/src/macros.h
+++ b/src/macros.h
@@ -261,7 +261,7 @@
 # define MESSAGE_QUEUE
 #endif
 
-#if defined(FEAT_EVAL) && defined(FEAT_FLOAT)
+#if defined(FEAT_EVAL)
 # include <float.h>
 # if defined(HAVE_MATH_H)
    // for isnan() and isinf()