Merge branch 'jk/avoid-redef-system-functions-2.30' into maint-2.39

Redefining system functions for a few functions did not follow our usual "implement git_foo() and #define foo(args) git_foo(args)" pattern, which has broken build for some folks. * jk/avoid-redef-system-functions-2.30: git-compat-util: undefine system names before redeclaring them git-compat-util: avoid redefining system function names