#568 string literal tail reuse

[Philipp Klaus Krause]

SDCC curently supports reuse of string literals: Identical string literals are the same object (within ech translation object). However ,t eh C standard allows even more reuse: When one string literal is identical to the postfix of another, the postfix could actually be used for the object.

Such cases are actually not that uncommon. In Dhrystone, we could save 91 bytes of string literals by doing such an optimization.

Philipp