Log Message:
gperftools: updated to 2.7

Changes 2.7:
bug in span stats printing introduced by new scalable page heap change was fixed.
Christoph Müllner has contributed couple warnings fixes and initial support for \ 
aarch64_ilp32 architecture.
Ben Dang contributed documentation fix for heap checker.
Fabrice Fontaine contributed fixed for linking benchmarks with --disable-static.
Holy Wu has added sized deallocation unit tests.
Holy Wu has enabled support of sized deallocation (c++14) on recent MSVC.
Holy Wu has fixed MSVC build in WIN32_OVERRIDE_ALLOCATORS mode.
Holy Wu has contributed cleanup of config.h used on windows.
Mao Huang has contributed couple simple tcmalloc changes from chromium code \ 
base. Making our tcmalloc forks a tiny bit closer.
issue 946 that caused compilation failures on some Linux clang installations has \ 
been fixed. Much thanks to github user htuch for helping to diagnose issue and \ 
proposing a fix.
Tulio Magno Quites Machado Filho has contributed build-time fix for PPC (for \ 
problem introduced in one of commits since RC).