Remove DEBUG_ASSERT_ASSUME()

It doesn't get completely discarded after all...

Fix foonathan#14: Incorrect Pragma

Release version 1.3.1

static_cast of the __LINE__ macro to unsigned type for instances wher…

…e __LINE__ might be of long type. (foonathan#8)

Update version

Use Clang __builtin_assume if available (foonathan#5)

* Using Clang __builtin_assume if available.

* Fixed warning in clang.

- Added an attribute to indicate that the assertion expression
is pure (as it should be).

Add clang-format file