Merge branch 'kd/mailinfo-quoted-string'

An author name, that spelled a backslash-quoted double quote in the
human readable part "My \"double quoted\" name", was not unquoted
correctly while applying a patch from a piece of e-mail.

* kd/mailinfo-quoted-string:
mailinfo: unescape quoted-pair in header fields
t5100-mailinfo: replace common path prefix with variable

diff --cc mailinfo.c
Simple merge

diff --cc t/t5100-mailinfo.sh
index e173c33f4b64480eaa948bc9f5e1178f82433f7f,45d228ebc81ed13c83d24f90895e9a374af5a87e..e6b995161e0fd15493bdaf4e5a5df2a3c2990798
--- 1/t/t5100-mailinfo.sh
--- 2/t/t5100-mailinfo.sh
+++ b/t/t5100-mailinfo.sh
@@@ -7,11 -7,13 +7,13 @@@ test_description='git mailinfo and git 
  
  . ./test-lib.sh
  
+ DATA="$TEST_DIRECTORY/t5100"
+ 
  test_expect_success 'split sample box' \
-       'git mailsplit -o. "$TEST_DIRECTORY"/t5100/sample.mbox >last &&
+       'git mailsplit -o. "$DATA/sample.mbox" >last &&
        last=$(cat last) &&
        echo total is $last &&
 -      test $(cat last) = 17'
 +      test $(cat last) = 18'
  
  check_mailinfo () {
        mail=$1 opt=$2