Add 'stm' package to the global package database

This is a preparation for `haskeline` picking up a dependency on `stm`
real soon now. See https://github.com/judah/haskeline/pull/61 for details.

If we figure out a way to not bundle the libraries depended upon by the
GHCi executable in the global package database (see #8919 for the original
reason why we had to start bundling terminfo/haskeline in the first place)
we can get rid of `stm` again...

On the bright side, we were able to avoid uploading new `stm` releases for
over two years already, so it shouldn't cause too much trouble if GHC imposes
a strong preference on the `stm` package's version (this most likely will
mostly affect Linux distributions & similiar).

While at it, this also update the stm submodule to include relaxed
bounds to allow the upcoming base-4.11 version.

ghc.mk

@@ -470,6 +470,7 @@ else
 libraries/haskeline_CONFIGURE_OPTS += --flags=-terminfo
 endif
 
+PACKAGES_STAGE1 += stm
 PACKAGES_STAGE1 += haskeline
 PACKAGES_STAGE1 += ghci
 

stm @ d65fd4de

-Subproject commit b6e863e517bdcc3c5de1fbcb776a3fd7e6fe2103
+Subproject commit d65fd4de49635a1e53405fe6699b46363a9d134e

packages

@@ -65,7 +65,7 @@ libraries/Win32              -           -                               https:/
 libraries/xhtml              -           -                               https://github.com/haskell/xhtml.git
 nofib                        nofib       -                               -
 libraries/parallel           extra       -                               ssh://git@github.com/haskell/parallel.git
-libraries/stm                extra       -                               -
+libraries/stm                -           -                               ssh://git@github.com/haskell/stm.git
 libraries/random             extra       -                               https://github.com/haskell/random.git
 libraries/primitive          dph         -                               https://github.com/haskell/primitive.git
 libraries/vector             dph         -                               https://github.com/haskell/vector.git