Add more out of memory checks (re: 18529b88) (#192)

The referenced commit neglected to add checks for strdup() calls.
That calls malloc() as well, and is used a lot.

This commit switches to another strategy: it adds wrapper functions
for all the allocation macros that check if the allocation
succeeded, so those checks don't need to be done manually.

src/cmd/ksh93/include/defs.h,
src/cmd/ksh93/sh/init.c:
- Add sh_malloc(), sh_realloc(), sh_calloc(), sh_strdup(),
  sh_memdup() wrapper functions with success checks. Call nospace()
  to error out if allocation fails.
- Update new_of() macro to use sh_malloc().
- Define new sh_newof() macro to replace newof(); it uses
  sh_realloc().

All other changed files:
- Replace the relevant calls with the wrappers.
- Remove now-redundant success checks from 18529b88.
- The ERROR_PANIC error message calls are updated to inclusive-or
  ERROR_SYSTEM into the exit code argument, so libast's error()
  appends the human-readable version of errno in square brackets.
  See src/lib/libast/man/error.3

src/cmd/ksh93/edit/history.c:
- Include "defs.h" to get access to the wrappers even if KSHELL is
  not defined.
- Since we're here, fix a compile error that occurred with KSHELL
  undefined by updating the type definition of hist_fname[] to
  match that of history.h.

src/cmd/ksh93/bltins/enum.c:
- To get access to sh_newof(), include "defs.h" instead of
  <shell.h> (note that "defs.h" includes <shell.h> itself).

src/cmd/ksh93/Mamfile:
- enum.c: depend on defs.h instead of shell.h.
- enum.o: add an -I. flag in the compiler invocation so that defs.h
  can find its subsequent includes.

src/cmd/builtin/pty.c:
- Define one outofmemory() function and call that instead of
  repeating the error message call.
- outofmemory() never returns, so remove superfluous exit handling.

Co-authored-by: Martijn Dekker <martijn@inlv.org>

src/cmd/ksh93/sh/macro.c

@@ -118,7 +118,7 @@ static int	charlen(const char*,int);
 
 void *sh_macopen(Shell_t *shp)
 {
-	void *addr = newof(0,Mac_t,1,0);
+	void *addr = sh_newof(0,Mac_t,1,0);
 	Mac_t *mp = (Mac_t*)addr;
 	mp->shp = shp;
 	return(addr);
@@ -971,9 +971,7 @@ static char *prefix(Shell_t *shp, char *id)
 				if(sub)
 					nv_putsub(np,sub,0L);
 			}
-			id = (char*)malloc(strlen(cp)+1+(n=strlen(sp=nv_name(np)))+ (sub?strlen(sub)+3:1));
-			if(!id)
-				sh_outofmemory();
+			id = (char*)sh_malloc(strlen(cp)+1+(n=strlen(sp=nv_name(np)))+ (sub?strlen(sub)+3:1));
 			memcpy(id,sp,n);
 			if(sub)
 			{
@@ -986,7 +984,7 @@ static char *prefix(Shell_t *shp, char *id)
 			return(id);
 		}
 	}
-	return(strdup(id));
+	return(sh_strdup(id));
 }
 
 /*
@@ -1041,7 +1039,7 @@ int sh_macfun(Shell_t *shp, const char *name, int offset)
 		t.node.com.comarg = &d.arg;
 		t.node.com.comline = shp->inlineno;
 		d.dol.dolnum = 1;
-		d.dol.dolval[0] = strdup(name);
+		d.dol.dolval[0] = sh_strdup(name);
 		stkseek(shp->stk,offset);
 		comsubst((Mac_t*)shp->mac_context,&t.node,2);
 		free(d.dol.dolval[0]);
@@ -1363,7 +1361,7 @@ retry1:
 					v = stkptr(stkp,mp->dotdot);
 					dolmax =1;
 					if(array_assoc(ap))
-						arrmax = strdup(v);
+						arrmax = sh_strdup(v);
 					else if((dolmax = (int)sh_arith(mp->shp,v))<0)
 						dolmax += array_maxindex(np);
 					if(type==M_SUBNAME)
@@ -1782,7 +1780,7 @@ retry1:
 			else
 				type = 0;
 		}
-		pattern = strdup(argp);
+		pattern = sh_strdup(argp);
 		if((type=='/' || c=='/') && (repstr = mac_getstring(pattern)))
 		{
 			Mac_t	savemac;
@@ -1794,7 +1792,7 @@ retry1:
 			mp->split = 0;
 			copyto(mp,0,0);
 			sfputc(stkp,0);
-			repstr = strdup(stkptr(stkp,n));
+			repstr = sh_strdup(stkptr(stkp,n));
 			replen = strlen(repstr);
 			stkseek(stkp,n);
 			*mp = savemac;
@@ -2165,9 +2163,7 @@ static void comsubst(Mac_t *mp,register Shnode_t* t, int type)
 			}
 			if(!(sp=mp->shp->sftable[fd]))
 			{
-				char *cp = (char*)malloc(IOBSIZE+1);
-				if(!cp)
-					sh_outofmemory();
+				char *cp = (char*)sh_malloc(IOBSIZE+1);
 				sp = sfnew(NIL(Sfio_t*),cp,IOBSIZE,fd,SF_READ|SF_MALLOC);
 			}
 			type = 3;