py/modmath: Implement math.isclose() for non-complex numbers.
As per PEP 485, this function appeared in for Python 3.5. Configured via
MICROPY_PY_MATH_ISCLOSE which is disabled by default, but enabled for the
ports which already have MICROPY_PY_MATH_SPECIAL_FUNCTIONS enabled.
diff --git a/ports/esp32/mpconfigport.h b/ports/esp32/mpconfigport.h
index 364b2de..cba3192 100644
--- a/ports/esp32/mpconfigport.h
+++ b/ports/esp32/mpconfigport.h
@@ -98,6 +98,7 @@
#define MICROPY_PY_COLLECTIONS_ORDEREDDICT (1)
#define MICROPY_PY_MATH (1)
#define MICROPY_PY_MATH_SPECIAL_FUNCTIONS (1)
+#define MICROPY_PY_MATH_ISCLOSE (1)
#define MICROPY_PY_CMATH (1)
#define MICROPY_PY_GC (1)
#define MICROPY_PY_IO (1)