Change-Id: Ieb77a7f2cdf765afa3121320d03c0478cd97eb0f

Document the fact that buffers are movable by default.
Care must be taken to not pass them to functions that yield().

Also clarify other things:
- Passing NULL as "ops" to buflib_alloc_ex() causes
  buffers to be movable by default (but not shrinkable).

- If you want shrinkable buffers during compaction,
  you have to provide a shrink callback.

- To disable buffer movement, you have to pass NULL
  for the move_callback inside the callback structure.

- The concept of default callbacks was removed
  long ago, remove the only reference of it.

Change-Id: I3bf0ea6b08b507d80a19f3c2c835aca32b3f7800

in micro-allocation scenarios.

Change-Id: I97a065bcfba8e0fda9b1670445e839e267c769c8

These 256K are intended to account for the binary size which reduces the total
available RAM on native targets. 256K is really outdated though, 768K should be
more accurate (for the majority of targets).

Change-Id: Iab3ee51d42ae15b1b7efb8588881579cf1948ae7

This should catch the case of buffer misuse which results
in corrupted cookie of next allocation. The check is performed
on move_block() so it may be a bit late.

There is buflib_check_valid() provided which checks the
integrity of all cookies for given context.
On DEBUG build with --sdl-thread this check is carried out
for core_ctx on every context switch to catch problems earlier.

Change-Id: I999d4576084592394e3dbd3bdf0f32935ff5f601
Reviewed-on: http://gerrit.rockbox.org/711
Reviewed-by: Thomas Martitz <kugel@rockbox.org>

buflib_allocatable() is what buflib_available() was before (it was in fact
simply renamed). It returns the largest contiguous block of memory. This
can be allocated and will definitely succeed, although larger allocations
may also succeed if the buffer can be compacted and shrinked.

buflib_available() now counts all free bytes, contiguous or not. This
better matches the description and how the caller use it.

Change-Id: I511e4eb5f4cf1821d957b3f4ef8a685ce40fe289
Reviewed-on: http://gerrit.rockbox.org/481
Reviewed-by: Thomas Martitz <kugel@rockbox.org>
Tested-by: Thomas Martitz <kugel@rockbox.org>

Only sdl app builds work properly for now.

Change-Id: I7807d42f69b8577b401e48cdc63de71e54f49217

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@31088 a1c6a512-1295-4272-9138-f99709370657

This allocation can be freed in the buflib debug menu (select it to free).
Doing a another allocation, e.g. by selecting another item in this debug menu
will cause compaction (all allocs move).

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@30719 a1c6a512-1295-4272-9138-f99709370657

This enables the ability to allocate (and free) memory dynamically
without fragmentation, through compaction. This means allocations can move
and fragmentation be reduced. Most changes are preparing Rockbox for this,
which many times means adding a move callback which can temporarily disable
movement when the corresponding code is in a critical section.

For now, the audio buffer allocation has a central role, because it's the one
having allocated most. This buffer is able to shrink itself, for which it
needs to stop playback for a very short moment. For this,
audio_buffer_available() returns the size of the audio buffer which can
possibly be used by other allocations because the audio buffer can shrink.

lastfm scrobbling and timestretch can now be toggled at runtime without
requiring a reboot.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@30381 a1c6a512-1295-4272-9138-f99709370657