Do not ever allow using the full line in preprocessor directives.

We would format:
  #define A \
    int f(a); int i;
as
  #define A \
    int f(a);\
    int i

The fix will break up macro definitions that could fit a line, but hit
the last column; fixing that is more involved, though, as it requires
looking at the following line.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@171715 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Format/Format.cpp b/lib/Format/Format.cpp
index 35c1e40..7b3c575 100644
--- a/lib/Format/Format.cpp
+++ b/lib/Format/Format.cpp
@@ -137,7 +137,7 @@
       // FIXME: We need to check whether we're in a preprocessor directive, even
       // if all tokens fit - the next line might be a preprocessor directive,
       // too, in which case we need to account for the possible escaped newline.
-      if (Columns > Style.ColumnLimit ||
+      if (Columns > Style.ColumnLimit - (Line.InPPDirective ? 1 : 0) ||
           (Annotations[i].MustBreakBefore &&
            Annotations[i].Type != TokenAnnotation::TT_CtorInitializerColon)) {
         FitsOnALine = false;