glibc: Fix of 3 CVEs

CVE-2018-6485: fix integer overflows in memalign and malloc - CVE-2018-1000001: fix realpath buffer underflow via getcwd - CVE-2018-19591: fix ifnametoindex descriptor leak...

CVE-2018-1000001

In glibc 2.26 and earlier there is confusion in the usage of getcwd by realpath which can be used to write before the destination buffer leading to a buffer underflow and potential code execution...