FIX: Canonizalize Windows path sep in xolox#misc#path#absolute().

On Windows, just converting to absolute paths is not enough to be able to use string-compare to test for equality. Depending on how it was constructed, the path may contain both forward- and backslashes (even a mix of them!) Therefore, canonicalize to what the 'shellslash' setting is set to.
Handle :normal! fold restore in session file.

A recent Vim 7.3 patch fixed the use of :normal to :normal! zo (so that mappings do not apply). Adapt the plugin's parsing to accommodate this.
Invoke autoload functions instead of defined custom commands.

Some people using the :Session... alternatives may :delcommand the original commands; in that case, the invocations by the script would fail. Prevent this error by invoking the autoload functions directly; this also obsoletes the need for fnameescape().
Avoid mandatory persistence of Vim size.

This does not affect the plugin's operation; rather, it is the author's preference. Therefore, honor the setting when it's in 'sessionoptions', but don't force it.
ENH: Ask to skip restoring for now, or delete the last-session.txt.

Change the check for restoring a previously persisted session so that there's a distinction between
"No": Then, Vim will not ask for restoring the session on subsequent startups. This is implemented by deleting the last-session.txt file.
"Skip": Do not restore the session now, but ask again on the next Vim startup (the old behavior).

Also, introduce a g:session_verbose_messages configuration variable; I found the hint how to disable the dialog distracting, because the long explanation makes it hard to focus on the actual decision.
ENH: Create session for current tab page only.

Depending on whether 'sessionoptions' contains "tabpages", GUI, font, features, colors, fullscreen are not persisted. Together with new :SaveTabSession, ... commands (only defined when the default 'sessionoptions' persist all tabs; otherwise, the original commands are enough and now work on single tab pages), this allows a more lightweight form of persistence limited to a single tab page. When such a single-tab session is restored, it also only deletes the buffers that were solely visible in the current tab page, and it replaces only the windows in that tab page. Additionally, a new :AppendTabSession command allows to add the session as a new tab page.

Public API functions xolox#session#is_tabsession() and xolox#session#session_name() have been added for use e.g. in 'titlestring'.

A limitation of the current implementation is that multiple (tab-only and/or global) sessions cannot be handled concurrently; due to the script-local variables, there's only a single notion of "current session", but that shouldn't matter that much in practice.
Skip the "save modified session" confirmation when re-opening the same.

When the current session is re-:OpenSession'ed again, the intention of the user is to revert to the saved state. No need to ask for persistence of the modifications, then. (This is like :edit! on a Vim buffer.)
Merge branch 'handle-changed-normal-persistence'
Merge branch 'avoid-own-command-use'
Merge branch 'avoid-mandatory-resize-persistence'
Merge branch 'enh-prompt-skip-or-delete'

Conflicts:
	autoload/xolox/session.vim
Merge branch 'enh-tabsession'

Conflicts:
	autoload/xolox/session.vim
Merge branch 'avoid-confirm-when-reopening'