Remove a weak_alias that results in a build error in some configs.

Notably, this was a build error for IMVU.
fix stringToC so it is parseable again
default emcc help to mention emcc, mention ./emcc just once
text update
Merge pull request #2749 from waywardmonkeys/fix-vfscanf-weak-alias

Remove a weak_alias that results in a build error in some configs.
fix emscripten ifdef
Merge pull request #2755 from hamishwillee/incoming

Incoming - additional index topics updated
text update
Update Documentation Home index - ready for review. Changes to other docs to support linking from this index.
Rename the Emscripten Browers Env. To Emscripten Runtime env. Put memory model doc into that doc. Update links to typed arrays mode 2 to point to the same place
Renamed file for browser env to runtime env. Fixes to links to support this
Integrated review comments for Module and File System API
Make side backgrounds light greyish rather than bright red.
Minor updates to all articles remaining wiki-import articles to fix obvious errors
Update the home page call to action box