Fix multiple bugs when using 'alias -p' to print aliases (#398)

This commit was originally intended to fix just one bug with shcomp's
handling of 'alias -p', but while fixing that I found a large number
of related issues in the alias command's -p, -t and -x options. The
current patch provides bugfixes for all of the bugs listed below:

1) Listing aliases in a script with 'alias -p' or 'alias' broke
   shcomp's bytecode output:
   https://github.com/ksh93/ksh/issues/87#issuecomment-813819122

2) Listing individual aliases with the -p option doesn't work:
      $ alias foo=bar bar=foo
      $ alias foo
      foo=bar
      $ alias -p foo  # No output

3) Listing specific tracked aliases with -pt does not display them
   in a reusable format, but rather adds another tracked alias:
      $ hash -r cat vi
      $ alias -pt vi  # No output
      $ alias -pt rm
      $ alias -t
      cat=/usr/bin/cat
      rm=/usr/bin/rm
      vi=/usr/bin/vi

4) Listing all tracked aliases with -pt does not output them in a
   reusable format (the resulting command printed only creates a
   normal alias, which is different from a tracked alias):
      $ hash -r cat
      $ alias -pt
      alias cat=/usr/bin/cat  # Expected 'alias -t cat'

5) Listing a non-existent alias with -p doesn't cause an error:
      $ unalias -a
      $ alias -p notanalias  # No output
      $ echo $?
      0
      $ alias notanalias
      notanalias: alias not found
      $ echo $?
      1
      $ hash -r
      $ alias -pt notacommand  # No output
      $ echo $?
      0

6) Attempting to list 256 non-existent aliases results in exit
   status zero:
      $ unalias -a
      $ alias $(awk -v ORS= 'BEGIN { for(i=0;i<256;i++) print "x "; }')
      x: alias not found
      --cut error message--
      $ echo $?
      0

Changes:

- typeset.c: Avoid printing anything while shcomp is compiling a
  script. This is needed because the alias command is run by shcomp
  to prevent parsing issues.

- b_alias(): To avoid adding tracked aliases with -pt, set
  tdata.aflag to '+' so that setall() and other related functions
  only list tracked aliases.

- b_alias(): Set tdata.pflag to 1 so that setall() and other
  functions recognize -p was passed.

- print_value(): Add support for listing specific aliases with
  'alias -p'.

- setall(): To avoid any issues with zombie tracked aliases (see also
  the regression tests) ignore tracked alias nodes marked with the
  NV_NOALIAS attribute. This bit is set for tracked alias nodes by
  the nv_rehash() function.

- setall(): For backward compatibility, continue incrementing the
  exit status for each invalid alias and tracked alias passed. This
  was already how alias behaved when listing aliases without -p, so
  using -p shouldn't cause a change in behavior:
      $ unalias -a
      $ alias foo bar
      foo: alias not found
      bar: alias not found
      $ echo $?
      2
  To fix bug 6, the exit status is set to one if an enforced 8-bit
  exit status would be zero.

- print_namval(): Set the prefix to 'alias -t' so that listing
  tracked aliases with 'alias -pt' works correctly.

- data/msg.c and include/name.h: Add an error message for when
  'alias -pt' doesn't find a tracked alias.

- tests/alias.sh: Add a ton of regression tests for the bugs fixed in
  this commit.

src/cmd/ksh93/include/version.h

@@ -21,7 +21,7 @@
 
 #define SH_RELEASE_FORK	"93u+m"		/* only change if you develop a new ksh93 fork */
 #define SH_RELEASE_SVER	"1.0.0-beta.2"	/* semantic version number: https://semver.org */
-#define SH_RELEASE_DATE	"2021-12-22"	/* must be in this format for $((.sh.version)) */
+#define SH_RELEASE_DATE	"2021-12-26"	/* must be in this format for $((.sh.version)) */
 #define SH_RELEASE_CPYR	"(c) 2020-2021 Contributors to ksh " SH_RELEASE_FORK
 
 /* Scripts sometimes field-split ${.sh.version}, so don't change amount of whitespace. */