Apply patches to build on DragonFly BSD and (older) FreeBSD

This now makes ksh build on DragonFly BSD.

bin/package, src/cmd/INIT/package.sh:
- DragonFly also needs the -lm hack for LDFLAGS.

src/cmd/ksh93/sh/main.c, src/cmd/ksh93/tests/basic.sh:
- fixargs() doesn't work on DragonFly either
  (re: 9b7c392a, 159fb9ee, cefe087d).

The following are backported from:
https://github.com/att/ast/issues/26#issuecomment-313927854
https://github.com/att/ast/pull/19

src/lib/libast/comp/setlocale.c:
- Add missing #include <errno.h> since errno is used.

src/lib/libast/features/standards:
- Do not set any standards macros (_POSIX_SOURCE etc) on FreeBSD or
  DragonflyBSD; they disable too much functionality on those.

src/lib/libast/features/wchar:
- Set _STDFILE_DECLARED on DragonFly, too.

src/lib/libast/include/sfio.h, src/lib/libast/include/sfio_t.h,
src/lib/libast/sfio/_sfopen.c, src/lib/libast/sfio/sfclrlock.c,
src/lib/libast/sfio/sfhdr.h, src/lib/libast/sfio/sfnew.c,
src/lib/libast/sfio/sfset.c:
- Rename SF_* macros to SFIO_* to avoid a conflict with system
  headers.

src/lib/libast/string/strexpr.c:
- Rename error() to err() to avoid a conflict.

src/cmd/ksh93/sh/main.c

@@ -52,7 +52,7 @@
 /* These routines are referenced by this module */
 static void	exfile(Shell_t*, Sfio_t*,int);
 static void	chkmail(Shell_t *shp, char*);
-#if defined(_lib_fork) && !defined(_NEXT_SOURCE) && !defined(__FreeBSD__) && !defined(__sun)
+#if defined(_lib_fork) && !defined(_NEXT_SOURCE) && !defined(__FreeBSD__) && !defined(__DragonFly__) && !defined(__sun)
     static void	fixargs(char**,int);
 #else
 #   define fixargs(a,b)
@@ -697,7 +697,7 @@ static void chkmail(Shell_t *shp, char *files)
 #   define PSTAT	1
 #endif
 
-#if defined(_lib_fork) && !defined(_NEXT_SOURCE) && !defined(__FreeBSD__) && !defined(__sun)
+#if defined(_lib_fork) && !defined(_NEXT_SOURCE) && !defined(__FreeBSD__) && !defined(__DragonFly__) && !defined(__sun)
 /*
  * fix up command line for ps command
  *