ecma_string_get_size performance improvemen - replace if with switch
ecma_string_get_size performance improvemen
- replace if with switch

JerryScript-DCO-1.0-Signed-off-by: Xin Hu Xin.A.Hu@intel.com

jerryscript-project/jerryscript,LeeHayun/jerryscript,jack60504/jerryscript,martijnthe/jerryscript,grgustaf/jerryscript,slaff/jerryscript,LeeHayun/jerryscript,glistening/jerryscript,martijnthe/jerryscript,LaszloLango/jerryscript,robertsipka/jerryscript,LaszloLango/jerryscript,gabrielschulhof/jerryscript,slaff/jerryscript,loki04/jerryscript,zherczeg/jerryscript,robertsipka/jerryscript,robertsipka/jerryscript,martijnthe/jerryscript,bsdelf/jerryscript,robertsipka/jerryscript,jerryscript-project/jerryscript,jack60504/jerryscript,grgustaf/jerryscript,jack60504/jerryscript,yichoi/jerryscript,tilmannOSG/jerryscript,loki04/jerryscript,jack60504/jerryscript,jack60504/jerryscript,gabrielschulhof/jerryscript,robertsipka/jerryscript,akosthekiss/jerryscript,bzsolt/jerryscript,tilmannOSG/jerryscript,jerryscript-project/jerryscript,bsdelf/jerryscript,bzsolt/jerryscript,slaff/jerryscript,LeeHayun/jerryscript,loki04/jerryscript,yichoi/jerryscript,glistening/jerryscript,loki04/jerryscript,akosthekiss/jerryscript,dbatyai/jerryscript,bsdelf/jerryscript,akosthekiss/jerryscript,LaszloLango/jerryscript,LeeHayun/jerryscript,glistening/jerryscript,dbatyai/jerryscript,akosthekiss/jerryscript,LaszloLango/jerryscript,loki04/jerryscript,gabrielschulhof/jerryscript,bzsolt/jerryscript,glistening/jerryscript,bsdelf/jerryscript,zherczeg/jerryscript,tilmannOSG/jerryscript,bsdelf/jerryscript,grgustaf/jerryscript,martijnthe/jerryscript,zherczeg/jerryscript,dbatyai/jerryscript,jerryscript-project/jerryscript,glistening/jerryscript,gabrielschulhof/jerryscript,martijnthe/jerryscript,bzsolt/jerryscript,slaff/jerryscript,tilmannOSG/jerryscript,tilmannOSG/jerryscript,zherczeg/jerryscript,loki04/jerryscript,yichoi/jerryscript,jack60504/jerryscript,bzsolt/jerryscript,yichoi/jerryscript,LaszloLango/jerryscript,martijnthe/jerryscript,grgustaf/jerryscript,grgustaf/jerryscript,gabrielschulhof/jerryscript,glistening/jerryscript,dbatyai/jerryscript,LeeHayun/jerryscript,jerryscript-project/jerryscript,grgustaf/jerryscript,robertsipka/jerryscript,akosthekiss/jerryscript,bsdelf/jerryscript,zherczeg/jerryscript,slaff/jerryscript,yichoi/jerryscript,dbatyai/jerryscript