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()
diff --git a/src/testdir/test_largefile.vim b/src/testdir/test_largefile.vim
index 1b3e02a..68d6ec9 100644
--- a/src/testdir/test_largefile.vim
+++ b/src/testdir/test_largefile.vim
@@ -24,11 +24,6 @@
   w
   " Check if the file size is 4,000,000,000 bytes.
   let fsize=getfsize(fname)
-  if has('num64')
-    call assert_true(fsize == 4000000000)
-  else
-    " getfsize() returns -2 if a Number is 32 bits.
-    call assert_true(fsize == -2)
-  endif
+  call assert_true(fsize == 4000000000)
   call delete(fname)
 endfunc
diff --git a/src/testdir/test_sort.vim b/src/testdir/test_sort.vim
index ce5592e..8299db4 100644
--- a/src/testdir/test_sort.vim
+++ b/src/testdir/test_sort.vim
@@ -1295,9 +1295,8 @@
   \                  '2147483647'], getline(1, '$'))
   bwipe!
 
-  if has('num64')
-    new
-    a
+  new
+  a
 -9223372036854775808
 -9223372036854775807
 
@@ -1312,22 +1311,21 @@
 abc
 
 .
-    sort n
-    call assert_equal(['',
-    \                  'abc',
-    \                  '',
-    \                  '-9223372036854775808',
-    \                  '-9223372036854775808',
-    \                  '-9223372036854775807',
-    \                  '-9223372036854775806',
-    \                  '-1',
-    \                  '0',
-    \                  '1',
-    \                  '9223372036854775806',
-    \                  '9223372036854775807',
-    \                  '9223372036854775807'], getline(1, '$'))
-    bwipe!
-  endif
+  sort n
+  call assert_equal(['',
+  \                  'abc',
+  \                  '',
+  \                  '-9223372036854775808',
+  \                  '-9223372036854775808',
+  \                  '-9223372036854775807',
+  \                  '-9223372036854775806',
+  \                  '-1',
+  \                  '0',
+  \                  '1',
+  \                  '9223372036854775806',
+  \                  '9223372036854775807',
+  \                  '9223372036854775807'], getline(1, '$'))
+  bwipe!
 endfunc
 
 
diff --git a/src/testdir/test_vimscript.vim b/src/testdir/test_vimscript.vim
index a75e5f6..b16b05b 100644
--- a/src/testdir/test_vimscript.vim
+++ b/src/testdir/test_vimscript.vim
@@ -1416,10 +1416,6 @@
 "-------------------------------------------------------------------------------
 
 func Test_num64()
-    if !has('num64')
-	return
-    endif
-
     call assert_notequal( 4294967296, 0)
     call assert_notequal(-4294967296, 0)
     call assert_equal( 4294967296,  0xFFFFffff + 1)
@@ -1692,27 +1688,15 @@
     " Test special cases: division or modulus with 0.
     let x = 1
     let x /= 0
-    if has('num64')
-        call assert_equal(0x7FFFFFFFFFFFFFFF, x)
-    else
-        call assert_equal(0x7fffffff, x)
-    endif
+    call assert_equal(0x7FFFFFFFFFFFFFFF, x)
 
     let x = -1
     let x /= 0
-    if has('num64')
-        call assert_equal(-0x7FFFFFFFFFFFFFFF, x)
-    else
-        call assert_equal(-0x7fffffff, x)
-    endif
+    call assert_equal(-0x7FFFFFFFFFFFFFFF, x)
 
     let x = 0
     let x /= 0
-    if has('num64')
-        call assert_equal(-0x7FFFFFFFFFFFFFFF - 1, x)
-    else
-        call assert_equal(-0x7FFFFFFF - 1, x)
-    endif
+    call assert_equal(-0x7FFFFFFFFFFFFFFF - 1, x)
 
     let x = 1
     let x %= 0