Make use of the align parameter attribute for all pointer arguments

We previously supported the align attribute on all (pointer) parameters, but we
only used it for byval parameters. However, it is completely consistent at the
IR level to treat 'align n' on all pointer parameters as an alignment
assumption on the pointer, and now we wll. Specifically, this causes
computeKnownBits to use the align attribute on all pointer parameters, not just
byval parameters. I've also added an explicit parameter attribute test for this
to test/Bitcode/attributes.ll.

And I've updated the LangRef to document the align parameter attribute (as it
turns out, it was not documented at all previously, although the byval
documentation mentioned that it could be used).

There are (at least) two benefits to doing this:
 - It allows enhancing alignment based on the pointer alignment after inlining callees.
 - It allows simplification of pointer arithmetic.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213670 91177308-0d34-0410-b5e6-96231b3b80d8
[ASan] Fix comments about __sanitizer_cov function

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213673 91177308-0d34-0410-b5e6-96231b3b80d8
Add LLVM_TOOLS_BINARY_DIR variable to LLVMConfig.cmake so clients
of LLVM using CMake can easily find the tools directory.

LLVM_BUILD_TOOLS_BINARY_DIR was removed because it is now
superfluous.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213674 91177308-0d34-0410-b5e6-96231b3b80d8