tools: Add one-time maintenance script.

This script only needs to be used this one time to transition from no-
squashing to squashing.  The only reason I'm committing it is to provide
crystal clear documentation of the steps I took to make the transition.

This script should never need to be unearthed again.
git: Remove core in prep for subtree add --squash.
Squashed 'jni/mupen64plus-core/' content from commit 73d693c

git-subtree-dir: jni/mupen64plus-core
git-subtree-split: 73d693c2d1119c261645a58b179b43c8f49d5f3f
core: Sync with upstream.
git: Remove ui-console in prep for subtree add --squash.
Squashed 'jni/mupen64plus-ui-console/' content from commit a04f4f2

git-subtree-dir: jni/mupen64plus-ui-console
git-subtree-split: a04f4f2b538ee1b39bf67553bff13703585cd1ea
ui-console: Sync with upstream.
git: Remove rsp-hle in prep for subtree add --squash.
Squashed 'jni/mupen64plus-rsp-hle/' content from commit 2022639

git-subtree-dir: jni/mupen64plus-rsp-hle
git-subtree-split: 202263954b0cf8870be469adc1f95c25f714bb58
rsp-hle: Sync with upstream.
git: Remove audio-sdl in prep for subtree add --squash.
Squashed 'jni/mupen64plus-audio-sdl/' content from commit 1fdacac

git-subtree-dir: jni/mupen64plus-audio-sdl
git-subtree-split: 1fdacac18e619e5b5adeacaec77df71790a292c7
audio-sdl: Sync with upstream.
git: Remove video-rice in prep for subtree add --squash.
Squashed 'jni/mupen64plus-video-rice/' content from commit e48c505

git-subtree-dir: jni/mupen64plus-video-rice
git-subtree-split: e48c50542b8388df361811ff41a4d17bed8c03db
video-rice: Sync with upstream.
tools: Remove one-time maintenance script.

This script only needs to be used this one time to transition from no-
squashing to squashing.  The only reason I'm committing it is to provide
crystal clear documentation of the steps I took to make the transition.

This script should never need to be unearthed again.
tools: Update pull-upstream script to squash from now on.
Merge branch 'squash-upstream-merges'