things were completely unusable due to security restriction in anything besides
xpcshell. This fixes bug 26879 and helps a lot for bug 8700 because is reduces
the work done for JSContext creation.
Also, ease the burden of xptcall porters by doing IS_COMPONENT for all unix platforms.
r=mccabe
git-svn-id: svn://10.0.0.236/trunk@60819 18797224-902f-48f8-a5cc-f745e15eee43