Add the float_power function in the brain and in its associated test

The bug pylint-dev/pylint#3319 was caused due to a missing function, named float_power inside the brain_numpy_core_umath module. This brain is used to infer all the numpy's ufunc functions. The problem is that in the website documentation of numpy, in the section that list all those functions, there is not entry dealing with the float_power function.

Also adds 5 missing functions detected by @texadactyl

Closes pylint-dev/pylint#3319

ChangeLog

@@ -6,6 +6,10 @@ What's New in astroid 2.4.0?
 ============================
 Release Date: TBA
 
+* Added some functions to the ``brain_numpy_core_umath`` module
+
+  Close PyCQA/pylint#3319
+
 * Added some functions of the ``numpy.core.multiarray`` module
 
   Close PyCQA/pylint#3208

astroid/brain/brain_numpy_core_umath.py

@@ -88,6 +88,7 @@ def __call__(self, x1, x2, {opt_args:s}):
     logical_not = FakeUfuncOneArg()
     modf = FakeUfuncOneArgBis()
     negative = FakeUfuncOneArg()
+    positive = FakeUfuncOneArg()
     rad2deg = FakeUfuncOneArg()
     reciprocal = FakeUfuncOneArg()
     rint = FakeUfuncOneArg()
@@ -106,13 +107,18 @@ def __call__(self, x1, x2, {opt_args:s}):
     bitwise_xor = FakeUfuncTwoArgs()
     copysign = FakeUfuncTwoArgs()
     divide = FakeUfuncTwoArgs()
+    divmod = FakeUfuncTwoArgs()
     equal = FakeUfuncTwoArgs()
+    float_power = FakeUfuncTwoArgs()
     floor_divide = FakeUfuncTwoArgs()
     fmax = FakeUfuncTwoArgs()
     fmin = FakeUfuncTwoArgs()
     fmod = FakeUfuncTwoArgs()
     greater = FakeUfuncTwoArgs()
+    gcd = FakeUfuncTwoArgs()
     hypot = FakeUfuncTwoArgs()
+    heaviside = FakeUfuncTwoArgs()
+    lcm = FakeUfuncTwoArgs()
     ldexp = FakeUfuncTwoArgs()
     left_shift = FakeUfuncTwoArgs()
     less = FakeUfuncTwoArgs()

tests/unittest_brain_numpy_core_umath.py

@@ -47,6 +47,7 @@ class NumpyBrainCoreUmathTest(unittest.TestCase):
         "logical_not",
         "modf",
         "negative",
+        "positive",
         "rad2deg",
         "reciprocal",
         "rint",
@@ -65,13 +66,18 @@ class NumpyBrainCoreUmathTest(unittest.TestCase):
         "bitwise_xor",
         "copysign",
         "divide",
+        "divmod",
         "equal",
+        "float_power",
         "floor_divide",
         "fmax",
         "fmin",
         "fmod",
+        "gcd",
         "greater",
+        "heaviside",
         "hypot",
+        "lcm",
         "ldexp",
         "left_shift",
         "less",