Rewrite some AST rules in tiger.g
Merge branch 'ast-rewrite-extend' of https://github.com/CS4240-tiger/tiger-compiler into ast-rewrite-extend

Conflicts:
	tiger.g
Rewrite many AST and grammar rules (#38)
Massive AST rewrite changes, grammar modifications, predicate use (#38)
Grammar changes; passes testcases 1,2,3,4,5,6,7,9,10 (#39)
INTLIT and FIXEDPTLIT now parse rules to properly handle MINUS
Fixed bug where an array can be declared with negative size
Grammar correctly fails testcases 8, 9 gracefully (#39)
Merge pull request #40 from CS4240-tiger/testcase-gram-check

Rewrite of grammar to pass testcases 1, 2, 3, 4, 5, 6, 7, 10 and gracefully fail 8, 9
Uncommented symbol table blocks; AST/syntactic predicate rewrite complete
Warning! Debug is now probably unusable in ANTLRWorks from now on!
Merge pull request #41 from CS4240-tiger/ast-rewrite-extend

Overhaul of AST generation, AST rewrite rules, syntactic predicates