TCSH: Update to 6.20.00.

[ng0]

[PATCH] gnu: tcsh: Update to 6.20.00.

This is almost fixed. Someone needs to look into failing test cases 131 and 188.

The tcsh-fix-autotest.patch was updated.
I compared the 6.19 version with 6.20 version of files and see no obvious 
reason for these to fail:

#                             -*- compilation -*-
131. subst.at:29: testing Filename substitution ...
./subst.at:44: tcsh -f files.csh
./subst.at:53: echo 'echo ~; echo "$HOME"' | tcsh -f | uniq | wc -l | tr -d ' 
\t'
./subst.at:57: echo "echo ~$(id -un)/foo; echo \"$HOME/foo\"" | tcsh -f | uniq  
  | wc -l | tr -d ' \t'
--- -   2017-01-08 23:36:16.461524744 +0000
+++ 
/tmp/guix-build-tcsh-6.20.00.drv-0/tcsh-6.20.00/testsuite.dir/at-groups/131/stdout
  2017-01-08 23:36:16.458666838 +0000
@@ -1,2 +1,2 @@
-1
+2

131. subst.at:29: 131. Filename substitution (subst.at:29): FAILED (subst.at:57)



#                             -*- compilation -*-
188. variables.at:707: testing $ cdtohome ...
./variables.at:708: tcsh -f -c 'cd'
--- /dev/null   2017-01-08 10:27:49.064082136 +0000
+++ 
/tmp/guix-build-tcsh-6.20.00.drv-0/tcsh-6.20.00/testsuite.dir/at-groups/188/stderr
  2017-01-08 23:36:18.990679394 +0000
@@ -0,0 +1 @@
+cd: Can't change to home directory.
./variables.at:708: exit code was 1, expected 0
188. variables.at:707: 188. $ cdtohome (variables.at:707): FAILED 
(variables.at:708)