Check that files are formatted correctly.

Fail the CI build if they are not.

.travis.yml

@@ -36,4 +36,5 @@ install:
 
 script:
   - $HOME/cache/astyle/build/gcc/bin/astyle --options=astylerc $(find . -name "*.[ch]")
+  - git diff --exit-code
   - make ENABLE_PYTHON=1 -j2

src/toxic.c

@@ -132,6 +132,7 @@ static void catch_SIGSEGV(int sig)
     if (!freopen("/dev/tty", "w", stderr)) {    // make sure stderr is enabled since we may have disabled it
         fprintf(stderr, "Warning: Failed to enable stderr\n");
     }
+
     endwin();
     fprintf(stderr, "Caught SIGSEGV: Aborting toxic session.\n");
     exit(EXIT_FAILURE);