typeset: Fix stack fencepost error, ISO C90 compat (#159)

src/cmd/ksh93/bltins/typeset.c:
- The new_argv[] array was one item too short (should be argc+2).
- Use AST stakalloc(3) to allocate it instead of a dynamic array;
  this restores compatibility with ISO C90.

src/lib/libast/features/standards, src/cmd/INIT/cc.unixware.i386:
- Add support for UnixWare.
- Do not define any standards macros on this system, as on FreeBSD
  and DragonFly BSD.

src/lib/libast/features/standards

@@ -6,9 +6,9 @@ set stdio
 # careful that we don't get fooled by presence of FreeBSD that underpins some
 # subsystems in Mac OS X; there are other Apple-specific portability hacks
 # elsewhere we should not interfere with.
-if tst note{ FreeBSD or DragonFly BSD }end compile{
+if tst note{ FreeBSD, DragonFly BSD, or UnixWare }end compile{
 		#include <sys/param.h>
-		#if (!defined(__FreeBSD__) && !defined(__DragonFly__)) || defined(APPLE)
+		#if (!defined(__FreeBSD__) && !defined(__DragonFly__) && !defined(__USLC__)) || defined(APPLE)
 		#error not a FreeBSD or DragonFly BSD system
 		#endif
 	}end {