"git config" did not provide a way to set or access numbers larger
than a native "int" on the platform; it now provides 64-bit signed
integers on all platforms.
* jk/config-int-range-check:
git-config: always treat --int as 64-bit internally
config: make numeric parsing errors more clear
config: set errno in numeric git_parse_* functions
config: properly range-check integer values
config: factor out integer parsing from range checks