Fix unnecessary parentheses warnings with GCC 8 [-Wparentheses]
Fix unnecessary parentheses warnings with GCC 8 [-Wparentheses]

Fixes the following GCC 8 warnings:
```
core/object.h:321:32: warning: unnecessary parentheses in declaration of '_get_get' [-Wparentheses]
core/object.h:331:32: warning: unnecessary parentheses in declaration of '_get_set' [-Wparentheses]
core/object.h:341:32: warning: unnecessary parentheses in declaration of '_get_get_property_list' [-Wparentheses]
core/object.h:360:32: warning: unnecessary parentheses in declaration of '_get_notification' [-Wparentheses]
core/object.h:517:32: warning: unnecessary parentheses in declaration of '_get_get' [-Wparentheses]
core/object.h:520:32: warning: unnecessary parentheses in declaration of '_get_set' [-Wparentheses]
core/object.h:523:32: warning: unnecessary parentheses in declaration of '_get_get_property_list' [-Wparentheses]
core/object.h:526:32: warning: unnecessary parentheses in declaration of '_get_notification' [-Wparentheses]
```

akien-mga/godot,pkowal1982/godot,Zylann/godot,ex/godot,BastiaanOlij/godot,Faless/godot,Valentactive/godot,Valentactive/godot,Zylann/godot,josempans/godot,Paulloz/godot,okamstudio/godot,guilhermefelipecgs/godot,vnen/godot,ex/godot,vnen/godot,ex/godot,sanikoyes/godot,Shockblast/godot,DmitriySalnikov/godot,honix/godot,groud/godot,ZuBsPaCe/godot,mcanders/godot,MarianoGnu/godot,okamstudio/godot,sanikoyes/godot,okamstudio/godot,okamstudio/godot,vkbsb/godot,pkowal1982/godot,DmitriySalnikov/godot,sanikoyes/godot,godotengine/godot,godotengine/godot,akien-mga/godot,akien-mga/godot,NateWardawg/godot,Valentactive/godot,Shockblast/godot,NateWardawg/godot,NateWardawg/godot,vnen/godot,Zylann/godot,vkbsb/godot,honix/godot,pkowal1982/godot,honix/godot,josempans/godot,vkbsb/godot,josempans/godot,sanikoyes/godot,akien-mga/godot,NateWardawg/godot,groud/godot,vkbsb/godot,Faless/godot,groud/godot,NateWardawg/godot,vkbsb/godot,godotengine/godot,Faless/godot,Shockblast/godot,Shockblast/godot,vnen/godot,MarianoGnu/godot,Valentactive/godot,godotengine/godot,Paulloz/godot,sanikoyes/godot,okamstudio/godot,BastiaanOlij/godot,ZuBsPaCe/godot,DmitriySalnikov/godot,josempans/godot,Faless/godot,Faless/godot,sanikoyes/godot,MarianoGnu/godot,ex/godot,BastiaanOlij/godot,godotengine/godot,josempans/godot,vnen/godot,MarianoGnu/godot,firefly2442/godot,firefly2442/godot,ex/godot,vnen/godot,josempans/godot,akien-mga/godot,guilhermefelipecgs/godot,ZuBsPaCe/godot,Paulloz/godot,MarianoGnu/godot,Zylann/godot,josempans/godot,BastiaanOlij/godot,DmitriySalnikov/godot,ZuBsPaCe/godot,Faless/godot,Paulloz/godot,sanikoyes/godot,sanikoyes/godot,mcanders/godot,NateWardawg/godot,Faless/godot,firefly2442/godot,Zylann/godot,Shockblast/godot,okamstudio/godot,MarianoGnu/godot,vkbsb/godot,Zylann/godot,NateWardawg/godot,guilhermefelipecgs/godot,Faless/godot,Shockblast/godot,Shockblast/godot,josempans/godot,guilhermefelipecgs/godot,NateWardawg/godot,pkowal1982/godot,guilhermefelipecgs/godot,pkowal1982/godot,vnen/godot,groud/godot,pkowal1982/godot,godotengine/godot,akien-mga/godot,godotengine/godot,Valentactive/godot,vkbsb/godot,firefly2442/godot,ZuBsPaCe/godot,Valentactive/godot,okamstudio/godot,vnen/godot,akien-mga/godot,ZuBsPaCe/godot,Paulloz/godot,firefly2442/godot,BastiaanOlij/godot,BastiaanOlij/godot,Valentactive/godot,BastiaanOlij/godot,godotengine/godot,okamstudio/godot,okamstudio/godot,guilhermefelipecgs/godot,DmitriySalnikov/godot,groud/godot,pkowal1982/godot,honix/godot,ex/godot,Paulloz/godot,vkbsb/godot,mcanders/godot,honix/godot,mcanders/godot,firefly2442/godot,Valentactive/godot,Zylann/godot,Paulloz/godot,ex/godot,pkowal1982/godot,mcanders/godot,NateWardawg/godot,ZuBsPaCe/godot,Zylann/godot,MarianoGnu/godot,mcanders/godot,akien-mga/godot,groud/godot,ex/godot,BastiaanOlij/godot,ZuBsPaCe/godot,MarianoGnu/godot,guilhermefelipecgs/godot,firefly2442/godot,firefly2442/godot,DmitriySalnikov/godot,DmitriySalnikov/godot,Shockblast/godot,honix/godot,guilhermefelipecgs/godot,okamstudio/godot