Require two c99 features (midblock decls, designated initializers)

c99 lets us do neat stuff like:

    {
      int j, k;
      foo(&j, &k);
      int z = j + k;
    }

and also
    struct point { int x; int y; };
    struct point pt = { .x=5, .y=5 };

This commit makes the configure scripts check to make sure your
compiler implements them.  It also disables our longstanding warning
about midblock declarations.

Closes ticket 13233.

1 files changed, 10 insertions, 0 deletions

diff --git a/changes/require-c99 b/changes/require-c99
new file mode 100644
index 0000000000..61d961273a
--- /dev/null
+++ b/changes/require-c99
@@ -0,0 +1,10 @@
+  o New compiler requirements:
+    - Tor 0.2.6.x requires that your compiler support more of the C99
+      language standard than before. The 'configure' script now detects
+      whether your compiler supports C99 mid-block declarations and
+      designated initializers. If it does not, Tor will not compile.
+
+      We may revisit this requirement if it turns out that a significant
+      number of people need to build Tor with compilers that don't
+      bother implementing a 15-year-old standard. Closes ticket 13233.
+