Fix checks on float literal exceeding max, and implicit float conversions.

test/test_suite/floats/explicit_float_truncation_needed.c3

@@ -0,0 +1,4 @@
+func void test()
+{
+    float x = 0x7FFFFFFFFFFF.0p+400; // #error: The value '3.63419e+134' is out of range for 'float', so you need an explicit cast to truncate the value
+}

test/test_suite/floats/float_exceeding_size.c3

@@ -0,0 +1,5 @@
+func void test()
+{
+    float x = 0x7FFFFFFFFFFF.0p+40000; // #error: The float value is out of range.
+
+}