autoconf: detect the broken bool in OpenWatcom 1.8

OpenWatcom 1.8 has a C99 mode, which implements _Bool and
<stdbool.h>.  Unfortunately the implementation is broken, and doesn't
let _Bool be implicitly converted to integer (as required by the C99
spec).  Detect this case in autoconf.

aclocal.m4

@@ -13,3 +13,27 @@ AC_DEFUN(PA_ADD_CFLAGS,
  AC_MSG_RESULT([no])
  CFLAGS="$pa_add_cflags__old_cflags")])
 
+dnl --------------------------------------------------------------------------
+dnl PA_WORKING_STDBOOL
+dnl
+dnl See if we have a working <stdbool.h> and bool support; in particular,
+dnl OpenWatcom 1.8 has a broken _Bool type that we don't want to use.
+dnl --------------------------------------------------------------------------
+AC_DEFUN(PA_WORKING_BOOL,
+[AC_MSG_CHECKING([if $CC has a working bool type])
+ AC_COMPILE_IFELSE(
+ [
+#ifndef __cplusplus
+#include <stdbool.h>
+#endif
+int foo(bool x, int y)
+{
+	return x+y;
+}
+ ],
+ [AC_MSG_RESULT([yes])
+  AC_DEFINE(HAVE_WORKING_BOOL, 1,
+    [Define to 1 if your compiler has a correct implementation of bool])],
+ [AC_MSG_RESULT([no])])
+])
+

compiler.h

@@ -78,7 +78,7 @@ int vsnprintf(char *, size_t, const char *, va_list);
 #endif
 
 #ifndef __cplusplus		/* C++ has false, true, bool as keywords */
-# ifdef HAVE_STDBOOL_H
+# if defined(HAVE_STDBOOL_H) && defined(HAVE_WORKING_BOOL)
 #  include <stdbool.h>
 # else
 /* This is sort of dangerous, since casts will behave different than

configure.in

@@ -97,6 +97,7 @@ AC_C_CONST
 AC_C_INLINE
 AC_C_RESTRICT
 AC_TYPE_SIZE_T
+PA_WORKING_BOOL
 AC_C_BIGENDIAN(AC_DEFINE(WORDS_BIGENDIAN),AC_DEFINE(WORDS_LITTLEENDIAN))
 AH_TEMPLATE(WORDS_BIGENDIAN,
 [Define to 1 if your processor stores words with the most significant