tests: Add some tests for bigint hash, float hash and float parsing.

Following outcome of recent fuzz testing and sanitizing by @jepler.

tests/basics/builtin_hash_intbig.py

@@ -8,3 +8,6 @@ class F:
     def __hash__(self):
         return 1 << 70 | 1
 print(hash(F()) != 0)
+
+# this had a particular error with internal integer arithmetic of hash function
+print(hash(6699999999999999999999999999999999999999999999999999999999999999999999) != 0)

tests/float/builtin_float_hash.py

@@ -3,6 +3,7 @@
 # these should hash to an integer with a specific value
 for val in (
     '0.0',
+    '-0.0',
     '1.0',
     '2.0',
     '-12.0',
@@ -15,6 +16,7 @@ for val in (
     '0.1',
     '-0.1',
     '10.3',
+    '0.4e3',
     '1e16',
     'inf',
     '-inf',

tests/float/float_parse.py

@@ -24,3 +24,9 @@ print(float('.' + '0' * 60 + '9e40') == float('9e-21'))
 print(float('1.00000000000000000000e-37'))
 print(float('10.0000000000000000000e-38'))
 print(float('100.000000000000000000e-39'))
+
+# very large exponent literal
+print(float('1e4294967301'))
+print(float('1e-4294967301'))
+print(float('1e18446744073709551621'))
+print(float('1e-18446744073709551621'))