On a target with a 16-bit mask (for example), we would choose the type
of an integer literal "1024" to be an int16. Previously, we used an int32,
which is a worse fit and leads to less efficient code than an int16
on a 16-bit mask target. (However, we'd still give an integer literal
1000000 the type int32, even in a 16-bit target.)
Updated the tests to still pass with 8 and 16-bit targets, given this
change.
Add a number of additional error cases in the grammar.
Enable bison's extended error reporting, to get better messages about the
context of errors and the expected (but not found) tokens at errors.
Improve the printing of these by providing an implementation of yytnamerr
that rewrites things like "TOKEN_MUL_ASSIGN" to "*=" in error messages.
Print the source location (using Error() when yyerror() is called; wiring
this up seems to require no longer building a 'pure parser' but having
yylloc as a global, which in turn led to having to update all of the uses of
it (which previously accessed it as a pointer).
Updated a number of tests_errors for resulting changesin error text.
