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/xec.c

@@ -626,7 +626,7 @@ static const Namdisc_t level_disc = {  sizeof(struct Level), put_level };
 
 static struct Level *init_level(Shell_t *shp,int level)
 {
-	struct Level *lp = newof(NiL,struct Level,1,0);
+	struct Level *lp = sh_newof(NiL,struct Level,1,0);
 	lp->maxlevel = level;
 	_nv_unset(SH_LEVELNOD,0);
 	nv_onattr(SH_LEVELNOD,NV_INT16|NV_NOFREE);
@@ -833,7 +833,7 @@ static int set_instance(Shell_t *shp,Namval_t *nq, Namval_t *node, struct Namref
 #endif /* SHOPT_NAMESPACE */
 	shp->instance = 1;
 	if((ap=nv_arrayptr(nq)) && (sp = nv_getsub(nq)))
-		sp = strdup(sp);
+		sp = sh_strdup(sp);
 	shp->instance = 0;
 	if(shp->var_tree!=shp->var_base && !nv_search((char*)nq,nr->root,HASH_BUCKET|HASH_NOSCOPE))
 	{
@@ -1119,7 +1119,7 @@ int sh_exec(register const Shnode_t *t, int flags)
 								if(!shp->strbuf2)
 									shp->strbuf2 = sfstropen();
 								sfprintf(shp->strbuf2,"%s%s%c",NV_CLASS,nv_name(shp->namespace),0);
-								shp->prefix = strdup(sfstruse(shp->strbuf2));
+								shp->prefix = sh_strdup(sfstruse(shp->strbuf2));
 								nv_open(shp->prefix,shp->var_base,NV_VARNAME);
 							}
 							else
@@ -1866,9 +1866,7 @@ int sh_exec(register const Shnode_t *t, int flags)
 				if((nsig=shp->st.trapmax*sizeof(char*))>0 || shp->st.trapcom[0])
 				{
 					nsig += sizeof(char*);
-					savsig = malloc(nsig);
-					if(!savsig)
-						sh_outofmemory();
+					savsig = sh_malloc(nsig);
 					memcpy(savsig,(char*)&shp->st.trapcom[0],nsig);
 					shp->st.otrapcom = (char**)savsig;
 				}
@@ -2686,7 +2684,7 @@ int sh_exec(register const Shnode_t *t, int flags)
 			else
 			{
 				nv_offattr(L_ARGNOD,NV_NOFREE);
-				shp->lastarg = strdup(comn);
+				shp->lastarg = sh_strdup(comn);
 			}
 		}
 		if(!skipexitset)
@@ -3112,12 +3110,10 @@ int sh_funscope(int argn, char *argv[],int(*fun)(void*),void *arg,int execflg)
 	/* save trap table */
 	if((nsig=shp->st.trapmax)>0 || shp->st.trapcom[0])
 	{
-		savsig = malloc(nsig * sizeof(char*));
-		if(!savsig)
-			sh_outofmemory();
+		savsig = sh_malloc(nsig * sizeof(char*));
 		/*
 		 * the data is, usually, modified in code like:
-		 *	tmp = buf[i]; buf[i] = strdup(tmp); free(tmp);
+		 *	tmp = buf[i]; buf[i] = sh_strdup(tmp); free(tmp);
 		 * so shp->st.trapcom needs a "deep copy" to properly save/restore pointers.
 		 */
 		for (isig = 0; isig < nsig; ++isig)
@@ -3125,7 +3121,7 @@ int sh_funscope(int argn, char *argv[],int(*fun)(void*),void *arg,int execflg)
 			if(shp->st.trapcom[isig] == Empty)
 				savsig[isig] = Empty;
 			else if(shp->st.trapcom[isig])
-				savsig[isig] = strdup(shp->st.trapcom[isig]);
+				savsig[isig] = sh_strdup(shp->st.trapcom[isig]);
 			else
 				savsig[isig] = NULL;
 		}
@@ -3169,7 +3165,7 @@ int sh_funscope(int argn, char *argv[],int(*fun)(void*),void *arg,int execflg)
 					np = nv_search(arg[r],shp->var_tree,HASH_NOSCOPE|NV_ADD);
 					if(np && (nq=*nref++))
 					{
-						np->nvalue.nrp = newof(0,struct Namref,1,0);
+						np->nvalue.nrp = sh_newof(0,struct Namref,1,0);
 						np->nvalue.nrp->np = nq;
 						nv_onattr(np,NV_REF|NV_NOFREE);
 					}