Replace 'thread safe' by 'thread-safe' in the documentation
diff --git a/ChangeLog b/ChangeLog
index d0bd377..d1e256e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -4,7 +4,7 @@
API Changes
* Extend the platform module with an abstraction mbedtls_platform_gmtime_r()
- whose implementation should behave as a thread safe version of gmtime().
+ whose implementation should behave as a thread-safe version of gmtime().
This allows users to configure such an implementation at compile time when
the target system cannot be deduced automatically, by setting the option
MBEDTLS_PLATFORM_GMTIME_R_ALT. At this stage Mbed TLS is only able to
