Use base allocator (tcmalloc) for V8 DLL

Normally, V8 is linked into the application and by virtue of that, it gets the
base allocator (tcmalloc).  However, since we are building V8 as a separate
DLL, we no longer get tcmalloc for V8.  This patch fixes this so that our V8
DLL will use tcmalloc instead of the standard Windows runtime heap.
Don't check for contractions when autocorrecting

This is to prevent "bad" autocorrections, like changing "i've" to "iv'e".
Althought "iv" and "e" are valid words according to the dictionary, so the
character-swap algorithm is working as designed, it causes more confusion to
the user than it is worth.

With this commit, things like "i've" will simply be marked as a misspelled word
instead of being corrected to "iv'e".  The user can easily right-click the word
and add it to their dictionary, or correct it to "I've".