use libc for lib/string and lib/memcopy

The glibc version can be in some cases 10 times faster than the kernel version

Signed-off-by: rachit-rc96 <rachit.rc96@gmail.com>
Tweak VM READAHEAD to 1024

One of the most important aspects of an operating system is the Virtual Memory Management system. Virtual Memory (VM) allows an operating system to perform many of its advanced functions, such as process isolation, file caching, and swapping. Tweaking it to 1024 can give a boost to read performance.

Signed-off-by: rachit-rc96 <rachit.rc96@gmail.com>