Revert "Revert "Turn off extern templates for most uses.""

The bionic tests on x86_64 are very unhappy about this:

external/gtest/include/gtest/gtest-printers.h:245: error: undefined reference to 'std::__1::basic_ostream<char, std::__1::char_traits<char> >::operator<<(__float128)'
external/gtest/include/gtest/gtest-printers.h:245: error: undefined reference to 'std::__1::basic_ostream<char, std::__1::char_traits<char> >::operator<<(__float128)'
external/gtest/include/gtest/gtest-printers.h:245: error: undefined reference to 'std::__1::basic_ostream<char, std::__1::char_traits<char> >::operator<<(__float128)'
external/gtest/include/gtest/gtest-printers.h:245: error: undefined reference to 'std::__1::basic_ostream<char, std::__1::char_traits<char> >::operator<<(__float128)'

I'll investigate tomorrow, but for now it's easiest to just revert.

This reverts commit 98c4e404ca.
Change-Id: I4c4e83be2ca465069734c54f4dcfa539916d35e4

include/__config

@@ -609,7 +609,7 @@ template <unsigned> struct __static_assert_check {};
 #endif
 
 #ifndef _LIBCPP_EXTERN_TEMPLATE
-#define _LIBCPP_EXTERN_TEMPLATE(...) extern template __VA_ARGS__;
+#define _LIBCPP_EXTERN_TEMPLATE(...)
 #endif
 
 #ifndef _LIBCPP_EXTERN_TEMPLATE2

src/algorithm.cpp

@@ -7,6 +7,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#define _LIBCPP_EXTERN_TEMPLATE(...) extern template __VA_ARGS__;
 #include "algorithm"
 #include "random"
 #include "mutex"

src/ios.cpp

@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "__config"
+
 #include "ios"
 #include "streambuf"
 #include "istream"

src/locale.cpp

@@ -7,6 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#define _LIBCPP_EXTERN_TEMPLATE(...) extern template __VA_ARGS__;
+
 // On Solaris, we need to define something to make the C99 parts of localeconv
 // visible.
 #ifdef __sun__

src/string.cpp

@@ -7,6 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#define _LIBCPP_EXTERN_TEMPLATE(...) extern template __VA_ARGS__;
+
 #include "string"
 #include "cstdlib"
 #include "cwchar"

src/valarray.cpp

@@ -7,6 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#define _LIBCPP_EXTERN_TEMPLATE(...) extern template __VA_ARGS__;
+
 #include "valarray"
 
 _LIBCPP_BEGIN_NAMESPACE_STD