Bug 968245 - Regenerate mozinfo.json as part of build backend; r=glandium

Previously, mozinfo.json was only generated as configure time.
Unfortunately, the build dependencies did not capture this relationship.
So, changes to mozinfo.py (or any supporting Python file) would not
trigger mozinfo regeneration, possibly leading to clobbers.

This patch moves mozinfo.json generation from the body of config.status
to the build backend. We had to add an AC_SUBST so the build config
knows when to build mozinfo.json. This was needed because js/src's build
system doesn't define all the required variables to create mozinfo.json.
Once js/src's configure/config.status is merged into the main build
config tree, this workaround can be removed.

While we were here, mozinfo.json was made to have consistent output and
its changes are now viewable with config.status --diff.

--HG--
extra : rebase_source : e91ed7173efdcde5831ae13b1ce69fc3cf32af97
extra : amend_source : 1610bcc6c3af764fdf685ee76188fb211bd828de
Bug 976054 - Fix XDR to store script->nslots_ with a uint32_t (r=wingo)
Bug 958596 - Allow gfx/2d/Logging.h to be used outside of gfx/2d. r=Bas

--HG--
extra : rebase_source : 7c99fccae55d8116f12b52ed74e178590c2c7414
Bug 958596 - Add support for gfx logging on android and b2g. r=Bas

--HG--
extra : rebase_source : 8d5a1c0dfc4f5f74e8417531b1f9f39c54e85d49
Bug 958596 - Add gfx logging support for 'char'. r=Bas

--HG--
extra : rebase_source : 2938fc27a6541fd5dd5ac1cf94f3e69ed3997ecc
Bug 958596 - Allow gfx logging of any rect, size, and point. r=Bas

--HG--
extra : rebase_source : b884b10446f5bc026285e6b16c202c7d9a2c377b
Bug 958596 - Allow writing a log statement that does not end in a newline. r=Bas

--HG--
extra : rebase_source : a26166451eb22c50b6bb32c2728bd07bdbf6e859
Bug 958596 - Add support a tree logging utility. r=Bas

--HG--
extra : rebase_source : 1bb9385ea2f9ce653ec0d5acd529edb63a385117
Bug 958596 - Allow TreeLog logging to be conditioned on a pref. r=Bas

--HG--
extra : rebase_source : 4390b6b07ec6cf195839f6e8386c769a8b234dd0
Bug 958596 - Add a Describe() method to nsIContent. r=bz

--HG--
extra : rebase_source : f0213fe5a8ad9dfba4b45ce27e731a748c104a91
Bug 958596 - Add a content description field to FrameMetrics and populate it if the apz.printtree pref is on. r=kats,tn

--HG--
extra : rebase_source : f009ad9d779fb1a3afa525fe7e5eb3a399aee628
Bug 958596 - Print the APZC tree for debugging. r=kats

--HG--
extra : rebase_source : bac86951246ba92f983a2ced3f7079143b5d42a1
Bug 958596 - Allow gfx logging of long long. r=Bas

--HG--
extra : rebase_source : c65c224a3ce6f09636be594eb68a95cc791841f7
Bug 958596 - Print ScrollableLayerGuids of APZCs when printing the tree. r=kats

--HG--
extra : rebase_source : cc3688109bb8a8a074e24b2f0268fdc556f05c1f
Bug 976151 - Anti eval/Function() check during wrapping should use |subsumes|. r=gabor
Backed out changeset 2912b402523d (bug 968245) for multiple test failures; CLOSED TREE
Backed out changeset 63d96f3e3e42 (bug 958596)
Backed out changeset 8e8db64bbaba (bug 958596)
Backed out changeset 7a16622e6b38 (bug 958596)
Backed out changeset a29e486e2214 (bug 958596)