Stop checking whether environ is declared.

There seems to be pretty good evidence that it's always declared,
and that checking for it is pointless.

Closes ticket 19142.

changes/19142

@@ -0,0 +1,3 @@
+  o Removed features:
+    - We no longer attempt to build on systems where 'environ' is not
+      declared in the C headers. Closes ticket 19142.

configure.ac

@@ -1533,17 +1533,6 @@ int main(int c, char **v) { puts(__FUNCTION__); }])],
   tor_cv_have_FUNCTION_macro=yes,
   tor_cv_have_FUNCTION_macro=no))
 
-AC_CACHE_CHECK([whether we have extern char **environ already declared],
-  tor_cv_have_environ_declared,
-  AC_COMPILE_IFELSE([AC_LANG_SOURCE([
-#ifdef HAVE_UNISTD_H
-#include <unistd.h>
-#endif
-#include <stdlib.h>
-int main(int c, char **v) { char **t = environ; }])],
-  tor_cv_have_environ_declared=yes,
-  tor_cv_have_environ_declared=no))
-
 if test "$tor_cv_have_func_macro" = "yes"; then
   AC_DEFINE(HAVE_MACRO__func__, 1, [Defined if the compiler supports __func__])
 fi
@@ -1557,11 +1546,6 @@ if test "$tor_cv_have_FUNCTION_macro" = "yes"; then
            [Defined if the compiler supports __FUNCTION__])
 fi
 
-if test "$tor_cv_have_environ_declared" = "yes"; then
-  AC_DEFINE(HAVE_EXTERN_ENVIRON_DECLARED, 1,
-           [Defined if we have extern char **environ already declared])
-fi
-
 # $prefix stores the value of the --prefix command line option, or
 # NONE if the option wasn't set.  In the case that it wasn't set, make
 # it be the default, so that we can use it to expand directories now.

src/common/compat.c

@@ -2390,15 +2390,6 @@ make_path_absolute(char *fname)
 #endif
 }
 
-#ifndef HAVE__NSGETENVIRON
-#ifndef HAVE_EXTERN_ENVIRON_DECLARED
-/* Some platforms declare environ under some circumstances, others don't. */
-#ifndef RUNNING_DOXYGEN
-extern char **environ;
-#endif
-#endif
-#endif
-
 /** Return the current environment. This is a portable replacement for
  * 'environ'. */
 char **