Log Message:
Update devel/gperftools to 2.4, patch provided by Jonathan Buschmann in PR 49625.

Changes from previous:

== 2.4 ==

+ enabled aggressive decommit option by default, significantly improve memory \ 
fragmentation
+ new ./configure flags for tcmalloc pagesize and tcmalloc allocation alignment.
+ Faster malloc/free, 5% on static library and about 10% on shared library. \ 
Mainly due to more efficient checking of malloc hooks.
+ Improved accuracy of stacktrace capturing in cpu profiler

== 2.3 ==

+ New experimental method for CPU profiling (only for Linux)
+ Most are fixes to pprof
+ Few other fixes, notably libunwind integration (selectable in configure step) \ 
and disabled on OSX & ppc64

== 2.2 ==

+ Support for mips/mips64/aarch64/ppc64-le
+ New method for capturing backtrace
+ More fixes
+ Fixes for Windows
+ Sources served by Google drive