New readme for this branch

README.cpl-gc

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+Copyright 2021 Holger Vogt
+New BSD license.
+
+A local garbage collector, especially cpl transmission line
+
+All memory allocation and deallocation are accompanied by functions from cplhash.c.
+Each time any memory is allocated, an entry is made into a hash table, storing the address.
+Each time memory is freed, this entry is removed again. Reallocation uses both procedures.
+Function mem_init() initializes the setup.
+Function mem_delete() frees all memory with addresses still found in the hash table.