More misc. tweaks and cleanups

Notable changes:

.github/workflows/ci.yml:
- Run 'bin/package test' on the github runner so we test iffe too.

src/cmd/ksh93/sh/subshell.c:
- sh_assignok was usually called like 'np = sh_assignok(np,0)'. But
  the function never changes np, it just returns the np value
  passed to it, so the assignment is pointless and that function
  can be changed to a void.

src/cmd/ksh93/sh/fault.c: sh_fault():
- Remove check for sh.subshell after sh_isstate(SH_INTERACTIVE). As
  of 48ba6964, it is never set in subshells.

src/lib/Mamfile

@@ -6,7 +6,6 @@ note * Mamfiles are processed by mamake (src/cmd/INIT/mamake.c); we added
 note * indentation to improve readability. The language is documented in
 note * src/cmd/INIT/README-mamake.md.
 note *
-note component level :MAKE: equivalent
 make test
 	make install
 		make all

src/lib/libast/features/common

@@ -25,10 +25,10 @@ tst	ptr_void note{ standard C void* ok }end compile{
 
 cat{
 	#pragma clang diagnostic ignored "-Wdeprecated-register"
-	#pragma clang diagnostic ignored "-Wmacro-redefined"
 	#pragma clang diagnostic ignored "-Wparentheses"
 	#pragma clang diagnostic ignored "-Wstring-plus-int"
 	#pragma clang diagnostic ignored "-Wunused-value"
+	#pragma GCC diagnostic ignored "-Wunused-result"
 
 	/* AST backwards compatibility macros */
 	#undef	_NIL_

src/lib/libast/man/error.3

@@ -242,19 +242,26 @@ ERROR_OPTIONS="system"
 provides debugging message macros when
 .L DEBUG
 or
-.L _TRACE_
+.L _BLD_DEBUG
 are defined
-.RL ( _TRACE_
+.RL ( _BLD_DEBUG
 is defined by
-.I makerules
-when
-.L CCFLAGS
-contains
-.LR \-g ).
+the
+.IR Mamfile s
+when the
+.L \-G
+a.k.a.
+.L \-\-debug\-symbols
+option is passed to
+.BR mamake (1),
+which the
+.BR package (1)
+command does automatically when given the argument
+.LR debug=1 ).
 All of the macros expand to nothing when both
 .L DEBUG
 and
-.L _TRACE_
+.L _BLD_DEBUG
 are not defined.
 Otherwise
 .L debug

src/lib/libast/path/pathpath.c

@@ -2,7 +2,7 @@
 *                                                                      *
 *               This software is part of the ast package               *
 *          Copyright (c) 1985-2012 AT&T Intellectual Property          *
-*          Copyright (c) 2020-2021 Contributors to ksh 93u+m           *
+*          Copyright (c) 2020-2022 Contributors to ksh 93u+m           *
 *                      and is licensed under the                       *
 *                 Eclipse Public License, Version 1.0                  *
 *                    by AT&T Intellectual Property                     *
@@ -76,7 +76,8 @@ pathpath_20100601(const char* p, const char* a, int mode, register char* path, s
 		{
 			if (*p != '/' && (mode & PATH_ABSOLUTE))
 			{
-				getcwd(buf, sizeof(buf));
+				if(!getcwd(buf, sizeof(buf)))
+					return (char*)0;
 				s = buf + strlen(buf);
 				sfsprintf(s, sizeof(buf) - (s - buf), "/%s", p);
 				if (path != buf)

src/lib/libcmd/wclib.c

@@ -2,7 +2,7 @@
 *                                                                      *
 *               This software is part of the ast package               *
 *          Copyright (c) 1992-2011 AT&T Intellectual Property          *
-*          Copyright (c) 2020-2021 Contributors to ksh 93u+m           *
+*          Copyright (c) 2020-2022 Contributors to ksh 93u+m           *
 *                      and is licensed under the                       *
 *                 Eclipse Public License, Version 1.0                  *
 *                    by AT&T Intellectual Property                     *
@@ -52,7 +52,6 @@
 #define eol(c)		((c)&WC_NL)
 #define mbc(c)		((c)&WC_MB)
 #define spc(c)		((c)&WC_SP)
-#define mb2wc(w,p,n)	(*ast.mb_towc)(&w,(char*)p,n)
 
 Wc_t* wc_init(int mode)
 {