Remove I_CAN_LIVE_WITH_LNK4049

Fixes #9332

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from #15649)

CHANGES.md

@@ -30,6 +30,12 @@ breaking changes, and mappings for the large list of deprecated functions.
 
 ### Changes between 1.1.1 and 3.0 [xx XXX xxxx]
 
+ * Version of MSVC earlier than 1300 could get link warnings, which could
+   be suppressed if the undocumented -DI_CAN_LIVE_WITH_LNK4049 was set.
+   Support for this flag has been removed.
+
+   *Rich Salz*
+
  * Rework and make DEBUG macros consistent. Remove unused -DCONF_DEBUG,
    -DBN_CTX_DEBUG, and REF_PRINT. Add a new tracing category and use it for
    printing reference counts. Rename -DDEBUG_UNUSED to -DUNUSED_RESULT_DEBUG

e_os.h

@@ -147,21 +147,6 @@ FILE *__iob_func();
 #     define stdin  (&__iob_func()[0])
 #     define stdout (&__iob_func()[1])
 #     define stderr (&__iob_func()[2])
-#    elif _MSC_VER<1300 && defined(I_CAN_LIVE_WITH_LNK4049)
-#     undef stdin
-#     undef stdout
-#     undef stderr
-         /*
-          * pre-1300 has __p__iob(), but it's available only in msvcrt.lib,
-          * or in other words with /MD. Declaring implicit import, i.e. with
-          * _imp_ prefix, works correctly with all compiler options, but
-          * without /MD results in LINK warning LNK4049: 'locally defined
-          * symbol "__iob" imported'.
-          */
-extern FILE *_imp___iob;
-#     define stdin  (&_imp___iob[0])
-#     define stdout (&_imp___iob[1])
-#     define stderr (&_imp___iob[2])
 #    endif
 #   endif
 #  endif