Back-ported commit ec6149f from 'alpha'; preparation for super-globals.
Restored v1 behaviour for dynamic variables.
Back-ported commit 853ccc4 from 'alpha'; implemented super-globals.
Add more VC++ files to .gitignore
Implement try/catch and throw, see notes below

Syntax (OTB style is supported):
  try
     OneLineOrBlock
  catch [OutputVar]
     OneLineOrBlock
  throw expression
If a try block does not have a catch block, the exception will be
"absorbed", i.e. it will resume execution after the try block.
ACT_THROW: Allocate sDerefBuf if it is NULL
Fix comment
Replace "Inappropiate line" error messages
Delete g.ThrownToken in global_clear_state() too
Get rid of EXCPT_THROWN
Revise handling of g->ThrownToken's memory
ACT_THROW: privatize sDerefBuf before calling ExpandExpression
Fix thrown string premature freeing
ACT_THROW: use the right Line structure
ACT_TRY: don't free non-NULL excpt token, and free mem_to_free too
Allow BIFs to throw exceptions
Disable non-expression "optimization" for ACT_THROW
Fix typo in ACT_TRY
Initialize aResult if a BIF throws an exception
Make Line::LineError() throw an exception if there's a try handler (for compatibility)