MFC r277396, r278681, r278865, r278924, r279205, r280208,

r280210, r280764 and r280768:

Update the Linux compatibility layer:

• Add more functions.
• Add some missing includes which are needed when the header files are not included in a particular order.
• The kasprintf() function cannot be inlined due to using a variable number of arguments. Move it to a C-file.
• Fix problems about 32-bit ticks wraparound and unsigned long conversion. Jiffies or ticks in FreeBSD have integer type and are not long.
• Add missing "order_base_2()" macro.
• Fix BUILD_BUG_ON() macro.
• Declare a missing symbol which is needed when compiling without -O2
• Clean up header file inclusions in the linux/completion.h, linux/in.h and linux/fs.h header files.

Sponsored by: Mellanox Technologies