add system calls to block and unblock a task

• avoiding a subtract with overflow

add syscalls to create cryptographicly secure random numbers

• add syscalls to create cryptographicly secure random numbers #96
• add integration tests
• avoid deadlock when multiple cores are available #106

add dependency to `Send` for the implementation of spinlock

• add requirement to use only types T for spinlocks, where the behavior Send is specified
• remove obsolete implementation of a irqsave refcell
• replace DoubleLinkedList by LinkedList of the alloc library
• using of the core collection library to handle memory and tasks
• the vector of PCI adapters aren't longer protected by a lock because these adapter are initialized at boot time. Afterwards, we have only read-access.
• Freelist: add check if a reunion with the previous slot is possible

remove dependency to rust feature "naked functions"

avoid bug in the nightly compiler by removing the dependency to the feature "naked functions"

improving the performance

• remove conflicts with the latest version of libstd

improve performace, revise network interface

• reduce the FPU interrupts
• revise network interface to impove the performance
• safer allocation/deallocation of the stack
• activate LTO support

remove deadlock, define log level at compile time

• extend pipeline to test the kernel (#40)
• remove deadlock in the implementation of conditional variables
• add option to set LevelFilter at compile time (#53)

v0.3.29

• add function to initialize CondQueue
• improve hypervisor detection, solve issue in nested virtualization environments

fix issue by determine the cpu frequency

• use for all system call the prefix sys_
• fix typos in the readme

separate stack for kernel / user space

• introduce page guards to protect the stacks
• remove compiler warnings
• ensure CpuFrequency is never explicitly set to zero (PR #29)