Fix and enable the autoconf test to allow the faster version of NS_LITERAL_STRING on compilers where sizeof(wchar_t) == 2 or compilers (such as gcc 2.96+) that accept -fshort-wchar to force this. r=waterson@netscape.com sr=cls@seawood.org b=54564

configure.in

@@ -1889,40 +1889,39 @@ fi
 dnl Check for short-wchar
 dnl ========================================================
 
-if test "$MOZ_ENABLE_SHORTWCHAR"
-then 
-
-AC_MSG_CHECKING(for size of wchar_t == 2)
-AC_TRY_RUN([ int main () {
-    if (sizeof(wchar_t) == 2) { return 0; } return 1; } ],
-        result="yes", result="no", result="maybe" )
-AC_MSG_RESULT("$result")
-if test "$result" = "yes"; then
+AC_CACHE_CHECK(for size of wchar_t == 2,
+    ac_cv_have_short_wchar_t,
+    [AC_TRY_RUN([#include <wchar.h>
+                 int main () { return (sizeof(wchar_t) != 2); } ],
+                ac_cv_have_short_wchar_t="yes",
+                ac_cv_have_short_wchar_t="no",
+                ac_cv_have_short_wchar_t="maybe")])
+if test "$ac_cv_have_short_wchar_t" = "yes"; then
     AC_DEFINE(HAVE_CPP_2BYTE_WCHAR_T)
     HAVE_CPP_2BYTE_WCHAR_T=1
-fi
-
-if test ! "$HAVE_CPP_2BYTE_WCHAR_T"
-then
+else
+dnl This is really gcc-only
     _SAVE_CFLAGS=$CFLAGS
     CFLAGS="$CFLAGS -fshort-wchar"
 
     AC_CACHE_CHECK(for compiler short-wchar option, 
-               ac_cv_have_short_wchar,
-               [AC_TRY_COMPILE(char *x;,
-                               char y,
-                               ac_cv_have_short_wchar=yes,
-                               ac_cv_have_short_wchar=no)])
+        ac_cv_have_short_wchar_t_option,
+        [AC_TRY_RUN([#include <wchar.h>
+                     int main () { return (sizeof(wchar_t) != 2); } ],
+                    ac_cv_have_short_wchar_t_option="yes",
+                    ac_cv_have_short_wchar_t_option="no",
+                    ac_cv_have_short_wchar_t_option="maybe")])
 
-    if test "$ac_cv_have_short_wchar" = "yes"; then
+    if test "$ac_cv_have_short_wchar_t_option" = "yes"; then
         AC_DEFINE(HAVE_CPP_2BYTE_WCHAR_T)
         HAVE_CPP_2BYTE_WCHAR_T=1
+dnl Is it OK to assume CXX and CC take the same arguments?
+        CXXFLAGS="$CXXFLAGS -fshort-wchar"
     else    
         CFLAGS=$_SAVE_CFLAGS
     fi
 fi
 
-fi
 dnl Checks for header files.
 dnl ========================================================
 AC_HEADER_DIRENT