patch 8.2.0155: warnings from MinGW compiler; tests fail without +float

Problem:    Warnings from MinGW compiler. (John Marriott) Json test fails when
            building without +float feature.
Solution:   Init variables. Fix Json parsing. Skip a few tests that require
            the +float feature.
diff --git a/src/if_py_both.h b/src/if_py_both.h
index 45bfeec..3da87cc 100644
--- a/src/if_py_both.h
+++ b/src/if_py_both.h
@@ -6357,8 +6357,8 @@
 					    ? "" : (char *)tv->vval.v_string);
 	case VAR_NUMBER:
 	    return PyLong_FromLong((long) tv->vval.v_number);
-#ifdef FEAT_FLOAT
 	case VAR_FLOAT:
+#ifdef FEAT_FLOAT
 	    return PyFloat_FromDouble((double) tv->vval.v_float);
 #endif
 	case VAR_LIST: