FileCheck: Add CHECK-SAME

FileCheck: Add CHECK-SAME

Add `CHECK-SAME`, which requires that the pattern matches on the *same*
line as the previous `CHECK`/`CHECK-NEXT` -- in other words, no newline
is allowed in the skipped region.  This is similar to `CHECK-NEXT`,
which requires exactly 1 newline in the skipped region.

My motivation is to simplify checking the long lines of LLVM assembly
for the new debug info hierarchy.  This allows CHECK sequences like the
following:

    CHECK:      ![[REF]] = !SomeMDNode(
    CHECK-SAME: file: ![[FILE:[0-9]+]]
    CHECK-SAME: otherField: 93{{[,)]}}

which is equivalent to:

    CHECK: ![[REF]] = !SomeMDNode({{.*}}file: ![[FILE:[0-9]+]]{{.*}}otherField: 93{{[,)]}}

While this example just has two fields, many nodes in debug info have
more than that.  `CHECK-SAME` will keep the logic easy to follow.

Morever, it enables interleaving `CHECK-NOT`s without allowing newlines.
Consider the following:

    CHECK:      ![[REF]] = !SomeMDNode(
    CHECK-SAME: file: ![[FILE:[0-9]+]]
    CHECK-NOT:  unexpectedField:
    CHECK-SAME: otherField: 93{{[,)]}}
    CHECK-NOT:  otherUnexpectedField:
    CHECK-SAME: )

which doesn't seem to have an equivalent `CHECK` line.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230612 91177308-0d34-0410-b5e6-96231b3b80d8