Remove unused constants

- Check for pthread_attr_getstack defines HAVE_PTHREAD_ATTR_GETSTACK
  which is not used in the code.
- ZEND_STACK_GROWS_DOWNWARDS is also not used in the code.

Author: petk

Zend/Zend.m4

@@ -146,7 +146,7 @@ _LT_AC_TRY_DLOPEN_SELF([
 ])
 
 dnl Checks for library functions.
-AC_CHECK_FUNCS(getpid kill sigsetjmp pthread_getattr_np pthread_attr_get_np pthread_get_stackaddr_np pthread_attr_getstack pthread_stackseg_np gettid)
+AC_CHECK_FUNCS(getpid kill sigsetjmp pthread_getattr_np pthread_attr_get_np pthread_get_stackaddr_np pthread_stackseg_np gettid)
 
 dnl Test whether the stack grows downwards
 dnl Assumes contiguous stack
@@ -169,7 +169,6 @@ int main(void) {
     return f((uintptr_t)&local) ? 0 : 1;
 }
 ]])], [
-  AC_DEFINE([ZEND_STACK_GROWS_DOWNWARDS], 1, [Define if the stack grows downwards])
   AC_DEFINE([ZEND_CHECK_STACK_LIMIT], 1, [Define if checking the stack limit is supported])
   AC_MSG_RESULT(yes)
 ], [

win32/build/config.w32

@@ -303,7 +303,6 @@ if (VS_TOOLSET && VCVERS >= 1914) {
 
 AC_DEFINE('HAVE_STRNLEN', 1);
 
-AC_DEFINE('ZEND_STACK_GROWS_DOWNWARDS', 1)
 AC_DEFINE('ZEND_CHECK_STACK_LIMIT', 1)
 
 ADD_SOURCES("main/streams", "streams.c cast.c memory.c filter.c plain_wrapper.c \