Fix typo in abs operator generation
Added test case for built-in operators
Added testcase to validate chaining of exit procedures
Refactor type analysis for procedure/output/operator calls
Added ceil/floor/trunc operators
Added special case for writeln/write operators
Refactor check_call function for computing the result type
Fix exit procedures in nested states
Use gcc instead of clang
Added sin/cos/sqrt/round operators
fix type analysis in call expressions with literal values
Merge remote-tracking branch 'upstream/master' into operators

Conflicts:
	tests/regression/Makefile
	tests/test.py
Rename imports
Order operators alphabetically
Fix typo
Change printf format string for integer types
Ada backend: added support for operators floor, ceil, round, and trunc
Ada backend: added cos, sin and sqrt