splitting asin tests out of test/agrad/agrad_test.cpp
splitting atan tests out of test/agrad/agrad_test.cpp
splitting atan2 tests out of test/agrad/agrad_test.cpp
splitting atan2 tests out of test/agrad/agrad_test.cpp
splitting atan2 tests out of test/agrad/agrad_test.cpp
splitting cosh tests out of test/agrad/agrad_test.cpp
splitting sinh tests out of test/agrad/agrad_test.cpp
splitting tanh tests out of test/agrad/agrad_test.cpp
splitting fabs tests out of test/agrad/agrad_test.cpp
splitting abs tests out of test/agrad/agrad_test.cpp
splitting floor tests out of test/agrad/agrad_test.cpp
splitting ceil tests out of test/agrad/agrad_test.cpp
splitting fmod tests out of test/agrad/agrad_test.cpp
splitting jacobian tests out of test/agrad/agrad_test.cpp
splitting free_memory tests out of test/agrad/agrad_test.cpp
splitting smart_pointer tests out of test/agrad/agrad_test.cpp
splitting stackAllocation tests out of test/agrad/agrad_test.cpp
leaving agrad_test.cpp for tests that rely on multiple operations
added manual entries for broadcast functions, rep_XXX()
moving stan/math/boost_error_handling to stan/math/error_handling/boost_error_handling