[LS] rethink document model and support variable types

[x87]

• declarations in included files should have line number of the INCLUDE directive (currently 0)
• support var..end and inline var
• support pre-processor directives (declaration may be unavailable)
  • Request: To Compile Identical Script for PC or Mobile dev#38
  • Conditional Compilation dev#144
• support scopes
  • Local Variable Scope dev#145
  • Scoped local variables in SCM scripts RFC dev#284
• support type inference
  • [DRAFT] Infer variable type using type information from SBL dev#257

[x87]

Symbol visibility boundary:

start

(this is where a symbol starts being visible)

• if a symbol is defined in an implicitly included file (such as constants.txt) its lower bound is 0
• if a symbol is defined in the current document its lower bound is the line of declaration statement (const ..., var ..., int... etc)
• if a symbol is defined in one of the $include'd files (and any descendants) its lower bound is the line of {$INCLUDE} in the current document

finish

(where a symbol stops being visible)

• for any symbol it is the end of current document
• if a symbol is defined inside a function, its upper bound is the function's end keyword
  • note that function bodies can be nested, and also the end keyword is ambiguous (could be used by loops or other blocks)