Add a Proxy C unittest (#3633)
Add a Proxy C unittest (#3633)

Previously only the Proxy api was tested.
Added a unittest to check the C callbacks via proxy.

JerryScript-DCO-1.0-Signed-off-by: Peter Gal pgal.u-szeged@partner.samsung.com
akosthekiss/jerryscript,robertsipka/jerryscript,robertsipka/jerryscript,dbatyai/jerryscript,bzsolt/jerryscript,robertsipka/jerryscript,dbatyai/jerryscript,dbatyai/jerryscript,bzsolt/jerryscript,jerryscript-project/jerryscript,akosthekiss/jerryscript,bzsolt/jerryscript,akosthekiss/jerryscript,zherczeg/jerryscript,jerryscript-project/jerryscript,zherczeg/jerryscript,bzsolt/jerryscript,zherczeg/jerryscript,bzsolt/jerryscript,robertsipka/jerryscript,jerryscript-project/jerryscript,jerryscript-project/jerryscript,dbatyai/jerryscript,dbatyai/jerryscript,jerryscript-project/jerryscript,zherczeg/jerryscript,akosthekiss/jerryscript,robertsipka/jerryscript,zherczeg/jerryscript,robertsipka/jerryscript,akosthekiss/jerryscript