vmtranslator/parser: use a map for segments instead of a slice in order to search an existence of a segment by O(1).
vmtranslator/parser: use a map for segments instead of a slice
in order to search an existence of a segment by O(1).

Signed-off-by: Soshi Katsuta <37be56e1b0b2d8665f687408a43d44ca133648fd@gmail.com>

skatsuta/nand2tetris,skatsuta/nand2tetris,skatsuta/nand2tetris