Clarifications and corrections to 1.5.0 release notes.

The main documentation did not link to git-remote documentation.

Clarified introductory text of git-rebase documentation.

Converted remaining mentions of update-index on Porcelain documents to git-add/git-rm.

Some i18n.* configuration variables were incorrectly described as core.*; fixed.

git-add and git-update-index on a filesystem on which executable bits are unreliable incorrectly reused st_mode bits even when the path changed between symlink and regular file.

git-daemon marks the listening sockets with FD_CLOEXEC so that it won’t be leaked into the children.

segfault from git-blame when the mandatory pathname parameter was missing was fixed; usage() message is given instead.

git-rev-list did not read $GIT_DIR/config file, which means that did not honor i18n.logoutputencoding correctly.

sliding mmap() inefficiently mmaped the same region of a packfile with an access pattern that used objects in the reverse order. This has been made more efficient.