patch 8.2.0271: the "num64" feature is available everywhere

Problem:    The "num64" feature is available everywhere and building without
            it causes problems.
Solution:   Graduage the "num64" feature. (James McCoy, closes #5650)
diff --git a/src/testdir/test_expr.vim b/src/testdir/test_expr.vim
index 1281ae7..7601c4f 100644
--- a/src/testdir/test_expr.vim
+++ b/src/testdir/test_expr.vim
@@ -382,9 +382,7 @@
 endfunc
 
 function Test_printf_64bit()
-  if has('num64')
-    call assert_equal("123456789012345", printf('%d', 123456789012345))
-  endif
+  call assert_equal("123456789012345", printf('%d', 123456789012345))
 endfunc
 
 function Test_printf_spec_s()
@@ -423,12 +421,8 @@
   call assert_equal(" 0b1111011", printf('%#10b', 123))
   call assert_equal("0B01111011", printf('%#010B', 123))
   call assert_equal("1001001100101100000001011010010", printf('%b', 1234567890))
-  if has('num64')
-    call assert_equal("11100000100100010000110000011011101111101111001", printf('%b', 123456789012345))
-    call assert_equal("1111111111111111111111111111111111111111111111111111111111111111", printf('%b', -1))
-  else
-    call assert_equal("11111111111111111111111111111111", printf('%b', -1))
-  endif
+  call assert_equal("11100000100100010000110000011011101111101111001", printf('%b', 123456789012345))
+  call assert_equal("1111111111111111111111111111111111111111111111111111111111111111", printf('%b', -1))
 endfunc
 
 func Test_substitute_expr()