Fixed fprintf arguments in tests
Updated build instructions
Make sure errcode is initialised
Expression creation test
Expression building tests
Tests for expression creation from handle arrays
Tests of expression properties
Consolidate handle array/expression tests into one test file
Forgot to advance iterator in subexpression creator
Subexpression tests
Rename expr_sub to expr_subexpr so as not to confuse it with a substitution test
Typo fix
Expression variables tests
Basic abbreviation creation API; no exports and imports yet