shcomp: fix redirection with process substitution

The commands within a process substitution used as an argument to a
redirection (e.g. < <(...) or > >(...)) are simply not included in
parse trees dumped by shcomp. This can be verified with a command
like hexdump -C. As a result, these process substitutions do not
work when running a bytecode-compiled shell script.

The fix is surprisingly simple. A process substitution is encoded
as a complete parse tree. When used with a redirection, that parse
tree is used as the file name for the redirection. All we need to
do is treat the "file name" as a parse tree instead of a string if
flags indicate a process substitution.

A process substitution is detected by the struct ionod field
'iofile'. Checking the IOPROCSUB bit flag is not enough. We also
need to exclude the IOLSEEK flag as that form of redirection may
use the IOARITH flag which has the same bit value as IOPROCSUB (see
include/shnodes.h).

src/cmd/ksh93/sh/tdump.c: p_redirect():
- Call p_tree() instead of p_string() for a process substitution.

src/cmd/ksh93/sh/trestore.c: r_redirect():
- Call r_tree() instead of r_string() for a process substitution.

src/cmd/ksh93/include/version.h:
- Bump the shcomp binary header version as this change is not
  backwards compatible; previous trestore.c versions don't know how
  to read the newly compiled process substitutions and would crash.

src/cmd/ksh93/tests/io.sh:
- Add test.

src/cmd/ksh93/tests/builtins.sh,
src/cmd/ksh93/tests/options.sh:
- Revert shcomp workarounds. (re: 6701bb30)

Resolves: https://github.com/ksh93/ksh/issues/165

src/cmd/ksh93/include/version.h

@@ -20,7 +20,7 @@
 
 #define SH_RELEASE_FORK	"93u+m"		/* only change if you develop a new ksh93 fork */
 #define SH_RELEASE_SVER	"1.0.0-alpha"	/* semantic version number: https://semver.org */
-#define SH_RELEASE_DATE	"2021-04-21"	/* must be in this format for $((.sh.version)) */
+#define SH_RELEASE_DATE	"2021-04-22"	/* 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. */
@@ -39,8 +39,5 @@
  * For shcomp: the version number (0-255) for the binary bytecode header.
  * Only increase very rarely, i.e.: if incompatible changes are made that
  * cause bytecode from newer versions to fail on older versions of ksh.
- *
- * The version number was last increased in 2021 for ksh 93u+m because
- * most of the predefined aliases were converted to builtin commands.
  */
-#define SHCOMP_HDR_VERSION	4
+#define SHCOMP_HDR_VERSION	5