Handle situations when cpp breaks a line into pieces.

There are situations in which GNU cpp breaks a single line of
input into multiple lines. These are indicated by linemarkers
that repeat the current line number, for instance:

  # 3 "file"
  this
  # 3  "file"
       is
  # 3  "file"
          all line three
  line four
  line five

We now remove these repeat linemarkers and collapse the
indicated lines back into one line, also eliminating the
leading whitespace that tries to preserve the column.

1 files changed, 9 insertions, 0 deletions

diff --git a/testcases b/testcases
index 091f19d..8b7dc81 100644
--- a/testcases
+++ b/testcases
@@ -161,3 +161,12 @@ abc'def
 BEGIN { print __cppawk_ver >= 20220318 }'
 :
 1
+--
+30:
+./cppawk  '
+#include <limits.h>
+BEGIN {
+  print INT_MIN, INT_MIN, INT_MIN
+}'
+:
+-2147483648 -2147483648 -2147483648