patch 8.0.0431: 'cinoptions' cannot set indent for extern block

Problem:    'cinoptions' cannot set indent for extern block.
Solution:   Add the "E" flag in 'cinoptions'. (Hirohito Higashi)

src/testdir/test_cindent.vim

@@ -14,3 +14,63 @@ func Test_cino_hash()
   call assert_equal(["#include <iostream>", "#include"], getline(1,2))
   bwipe!
 endfunc
+
+func Test_cino_extern_c()
+  " Test for cino-E
+
+  let without_ind = [
+        \ '#ifdef __cplusplus',
+        \ 'extern "C" {',
+        \ '#endif',
+        \ 'int func_a(void);',
+        \ '#ifdef __cplusplus',
+        \ '}',
+        \ '#endif'
+        \ ]
+
+  let with_ind = [
+        \ '#ifdef __cplusplus',
+        \ 'extern "C" {',
+        \ '#endif',
+        \ "\tint func_a(void);",
+        \ '#ifdef __cplusplus',
+        \ '}',
+        \ '#endif'
+        \ ]
+  new
+  setlocal cindent cinoptions=E0
+  call setline(1, without_ind)
+  call feedkeys("gg=G", 'tx')
+  call assert_equal(with_ind, getline(1, '$'))
+
+  setlocal cinoptions=E-s
+  call setline(1, with_ind)
+  call feedkeys("gg=G", 'tx')
+  call assert_equal(without_ind, getline(1, '$'))
+
+  setlocal cinoptions=Es
+  let tests = [
+        \ ['recognized', ['extern "C" {'], "\t\t;"],
+        \ ['recognized', ['extern "C++" {'], "\t\t;"],
+        \ ['recognized', ['extern /* com */ "C"{'], "\t\t;"],
+        \ ['recognized', ['extern"C"{'], "\t\t;"],
+        \ ['recognized', ['extern "C"', '{'], "\t\t;"],
+        \ ['not recognized', ['extern {'], "\t;"],
+        \ ['not recognized', ['extern /*"C"*/{'], "\t;"],
+        \ ['not recognized', ['extern "C" //{'], ";"],
+        \ ['not recognized', ['extern "C" /*{*/'], ";"],
+        \ ]
+
+  for pair in tests
+    let lines = pair[1]
+    call setline(1, lines)
+    call feedkeys(len(lines) . "Go;", 'tx')
+    call assert_equal(pair[2], getline(len(lines) + 1), 'Failed for "' . string(lines) . '"')
+  endfor
+
+
+
+  bwipe!
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab