Update files that depend on unixfork functions to include unixfork.h
Declare as static all functions in unixfork.c that are not needed externally.
Add dependencies to makefile-tail.
modified: makefile-tail
new file: ../inc/unixfork.h
modified: ../src/ldeboot.c
modified: ../src/main.c
modified: ../src/unixfork.c