Use new --match-full-lines FileCheck feature for Preprocessor/init.c.

This required fixing a few check lines which had omitted trailing
characters, and were passing incorrectly (e.g., asserting that
__UINT64_C_SUFFIX__ is "UL" instead of the "ULL" that it actually is set
to). All were obviously broken tests, not broken code.

llvm-svn: 260542