fix: replace -ansi with -std=gnu89 in Concorde build

-ansi disables POSIX extensions, breaking builds on modern Linux
(h_addr macro unavailable, gethostname signature mismatch).
-std=gnu89 enforces C89 syntax while keeping POSIX/GNU extensions.

Fixes #79, fixes #84.

Author: jvkersch

setup.py

@@ -91,7 +91,7 @@ def build_concorde():
         print("building concorde")
         _run("tar xzvf concorde.tgz", "build")
 
-        cflags = "-fPIC -O2 -g -ansi"
+        cflags = "-fPIC -O2 -g -std=gnu89"
 
         if platform.system().startswith("Darwin"):
             flags = "--host=darwin"