Rename DFG's compileAdd to compileArithAdd.

Rename DFG's compileAdd to compileArithAdd.
https://bugs.webkit.org/show_bug.cgi?id=150866

Reviewed by Benjamin Poulain.

The function is only supposed to generate code to do arithmetic addition on
numeric types.  Naming it compileArithAdd() is more accurate, and is consistent
with the name of the node it emits code for (i.e. ArithAdd) as well as other
compiler functions for analogous operations e.g. compileArithSub.

* dfg/DFGSpeculativeJIT.cpp:
(JSC::DFG::SpeculativeJIT::compileInstanceOf):
(JSC::DFG::SpeculativeJIT::compileArithAdd):
(JSC::DFG::SpeculativeJIT::compileAdd): Deleted.
* dfg/DFGSpeculativeJIT.h:
* dfg/DFGSpeculativeJIT32_64.cpp:
(JSC::DFG::SpeculativeJIT::compile):
* dfg/DFGSpeculativeJIT64.cpp:
(JSC::DFG::SpeculativeJIT::compile):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@192000 268f45cc-cd09-0410-ab3c-d52691b4dbfc