Merge branch '87283f04-c2e1-4a5b-b9c6-a7c5ed0ef381' into 'master'

replace vmalloc with system allocator (malloc)

Closes #1757 and #1603

See merge request graphviz/graphviz!1460

diff --cc CHANGELOG.md
index a51850948b2424284c7fb6cd40d3c636a3fb5753,c5bf448bb9371520f50da05a009972de8aa1d101..11341b13c7bb1e2d7decdd236c832de7505a660e
--- 1/CHANGELOG.md
--- 2/CHANGELOG.md
+++ b/CHANGELOG.md
@@@ -5,12 -5,8 +5,13 @@@ The format is based on [Keep a Changelo
  and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
  
  ## [Unreleased]
+ - Cgraph's agheap() API has been removed
  
 +### Fixed
 +- gvpr: line numbers in gvpr errors/warnings are incorrect #1594
 +- URL typo in patchwork man page
 +- Escaped backslashes are not correctly handled when producing xdot with dot #165
 +
  ## [2.44.1] - 2020-06-29
  
  ### Added