tests: fix syncline tests

These tests are skipped with GCC:

    "\"".c:1:5: error: function declaration isn't a prototype [-Werror=strict-prototypes]
     int main() { return 0; }
         ^~~~

* tests/synclines.at: Stop writing C++ in C.
* tests/local.at: Formatting changes.

tests/local.at

@@ -940,11 +940,11 @@ m4_define([AT_SKIP_IF_EXCEPTION_SUPPORT_IS_POOR],
 [[#include <iostream>
 #include <stdexcept>
 
-void foo()
+void foo ()
 {
   try
     {
-      throw std::runtime_error("foo");
+      throw std::runtime_error ("foo");
     }
   catch (...)
     {
@@ -953,11 +953,11 @@ void foo()
     }
 }
 
-int main()
+int main ()
 {
   try
     {
-      foo();
+      foo ();
     }
   catch (...)
     {

tests/synclines.at

@@ -396,7 +396,7 @@ AT_BISON_OPTION_PUSHDEFS([%skeleton "$1"])
 # properly to the linker, and is unable to save a file named this way.
 # Don't try with such compilers.
 AT_DATA([\"\\\"\".c],
-[[int main() { return 0; }
+[[int main (void) { return 0; }
 ]])
 
 AT_CHECK([AT_CXX_IF([$CXX $CXXFLAGS], [$CC $CFLAGS]) $CPPFLAGS \"\\\"\".c -o \"\\\"\" ||