Add ChangeLog entry for dylib builds using Makefile
mbed TLS ChangeLog (Sorted per branch, date)
+= mbed TLS x.x.x branch released xxxx-xx-xx
+
+Bugfix
+ * Fix dynamic library building process with Makefile on Mac OS X. Fixed by
+ mnacamura.
+
= mbed TLS 2.7.0 branch released 2018-02-03
Security
