Provide more efficient implementation(s) of at:ifPresent:ifAbsent: given impending use in the Compiler.
=============== Diff against Kernel-ul.1157 ===============
Item was added:
+ ----- Method: MethodDictionary>>at:ifPresent:ifAbsent: (in category 'accessing') -----
+ at: key ifPresent: oneArgBlock ifAbsent: absentBlock
+ "Lookup the given key in the receiver. If it is present, answer the
+ value of evaluating the oneArgBlock with the value associated
+ with the key, otherwise answer the value of absentBlock."
+ ^(array at: (self scanFor: key))
+ ifNil: [absentBlock value]
+ ifNotNil: [:method| oneArgBlock value: method]!