add configure option to run tests without valgrind

configure.ac

@@ -83,6 +83,12 @@ AC_CHECK_FUNCS(memmem)
 AC_CHECK_FUNCS(mkstemp)
 
 
+dnl Running tests with Valgrind is slow. It is faster to iterate on
+dnl code without Valgrind until tests pass, then enable Valgrind and
+dnl fix leaks.
+AC_ARG_ENABLE([valgrind],
+   AC_HELP_STRING([--disable-valgrind], [do not run tests under Valgrind]))
+
 dnl Don't attempt to build docs if there's no Ruby lying around
 AC_ARG_ENABLE([docs],
    AC_HELP_STRING([--disable-docs], [don't build docs]))
@@ -119,6 +125,7 @@ EOF
    fi
 ])
 
+AM_CONDITIONAL([ENABLE_VALGRIND], [test "x$enable_valgrind" != xno])
 AM_CONDITIONAL([ENABLE_DOCS], [test "x$enable_docs" != xno])
 AM_CONDITIONAL([ENABLE_ERROR_INJECTION], [test "x$enable_error_injection" = xyes])
 AM_CONDITIONAL([ENABLE_ALL_STATIC], [test "x$enable_all_static" = xyes])