New function for testing if buffer is narrowed

Also fix simple-call-tree-jump-to-function-at-point so that
it works with narrowing

Altered items:
simple-call-tree-jump-to-function-at-point,
simple-call-tree-buffer-narrowed-p, simple-call-tree-narrow-to-subtree
New movement functions: up & next/prev samelevel

Also major-mode keybindings for these.

Altered items:
simple-call-tree-mode, simple-call-tree-move-up,
simple-call-tree-move-next, simple-call-tree-move-prev,
simple-call-tree-move-next-samelevel,
simple-call-tree-move-prev-samelevel,
simple-call-tree-buffer-narrowed-p
New major-mode keybinding for burying the buffer

Altered items:
simple-call-tree-mode
New function simple-call-tree-get-function-at-point

Also alter simple-call-tree-display-function-at-point
and simple-call-tree-jump-to-function-at-point to use
the new function.

Altered items:
simple-call-tree-get-function-at-point,
simple-call-tree-display-function-at-point,
simple-call-tree-jump-to-function-at-point
Keep narrowed status after jumping/inverting buffer

Make sure buffer is narrowed/widened in the same way after calls
to simple-call-tree-invert-buffer or
simple-call-tree-jump-to-function-at-point

Altered items:
simple-call-tree-invert-buffer,
simple-call-tree-jump-to-function-at-point
Alteration to simple-call-tree-jump-to-function-at-point

Change name to simple-call-tree-jump-to-function and allow choosing
function using ido when called interactively with prefix arg.

Altered items:
simple-call-tree-default-recenter, simple-call-tree-mode,
simple-call-tree-invert-buffer, simple-call-tree-jump-to-function
Rename simple-call-tree-display-function-at-point

Rename it to simple-call-tree-display-function

Altered items:
simple-call-tree-mode, simple-call-tree-display-function
Alter simple-call-tree-display-function

Make it behave like simple-call-tree-jump-to-function for choosing
which func to display.

Altered items:
simple-call-tree-display-function, simple-call-tree-jump-to-function
New function simple-call-tree-goto-function and keybindings

New function for moving to function at point, and new major-mode
keybindings.

Altered items:
simple-call-tree-mode, simple-call-tree-goto-function,
simple-call-tree-jump-to-function
Alter simple-call-tree-analyze to save locations

Markers of function definition locations are saved to
simple-call-tree-locations.

Altered items:
simple-call-tree-locations, simple-call-tree-analyze
New function simple-call-tree-current-function

Also alter simple-call-tree-get-function-at-point so that it works with
other buffers (when given the buffer as an argument).

Altered items:
simple-call-tree-current-function,
simple-call-tree-get-function-at-point
Fixes to simple-call-tree-current-function and others

Also some documentation changes.

Altered items:
simple-call-tree-display-buffer,
simple-call-tree-current-function,
simple-call-tree-get-function-at-point
Rename simple-call-tree-narrow-to-subtree

Rename it to simple-call-tree-toggle-narrowing, also
change behaviour so that it takes an optional prefix key
argument to specify narrow/widen (instead of toggle).

Altered items:
simple-call-tree-mode, simple-call-tree-current-function,
simple-call-tree-invert-buffer, simple-call-tree-jump-to-function,
simple-call-tree-toggle-narrowing
Narrow buffer when simple-call-tree-current-function called.

Also add extra arg WIDE to tell simple-call-tree-current-function
to widen the *Simple Call Tree* buffer.

Altered items:
simple-call-tree-current-function
Use markers to display/visit functions

Use simple-call-tree-locations alist to find function locations.

Altered items:
simple-call-tree-display-function, simple-call-tree-goto-function
Rename variables and functions

Rename:
  simple-call-tree-locations to simple-call-tree-locations-alist
  simple-call-tree-display-function to simple-call-tree-view-function
  simple-call-tree-goto-function to simple-call-tree-visit-function

Altered items:
simple-call-tree-mode, simple-call-tree-locations,
simple-call-tree-locations-alist, simple-call-tree-analyze,
simple-call-tree-view-function, simple-call-tree-visit-function
Integrate with fm-mode

Alter simple-call-tree-visit-function to work with fm-mode by making
arg optional.
Add cons cell to fm-modes, and add fm-start to simple-call-tree-mode-hook.

Altered items:
simple-call-tree-visit-function, simple-call-tree-mode-hook
Change outline headings

Set outline-regexp in simple-call-tree-mode and change functions
to make outline headings look a bit nicer.

Altered items:
simple-call-tree-mode, simple-call-tree-current-maxdepth,
simple-call-tree-display-buffer,
simple-call-tree-list-callers-and-functions,
simple-call-tree-list-callees-recursively,
simple-call-tree-change-maxdepth,
simple-call-tree-get-function-at-point,
simple-call-tree-jump-to-function, simple-call-tree-toggle-narrowing
Rearrange code: move simple-call-tree-get-function-at-point

Also slight changes to simple-call-tree-change-maxdepth
(further changes to come).

Altered items:
simple-call-tree-change-maxdepth,
Set outline-level function, and change depth to start at 1

Set outline-level in *Simple Call Tree* buffer new function
simple-call-tree-outline-level. Alter outline-regexp so that it
captures the arrow in a match-string which is then used to determine
the depth with simple-call-tree-outline-level.
Change all references and assignments to depth so that level 1
is the top level.

Altered items:
simple-call-tree-mode, simple-call-tree-display-buffer,
simple-call-tree-list-callers-and-functions,
simple-call-tree-list-callees-recursively,
simple-call-tree-outline-level, simple-call-tree-invert-buffer,
simple-call-tree-change-maxdepth