[glibc] malloc - checks

[malloc] fastbins size check

[malloc] smallbins bk check & unlink

[malloc] unsorted bin size check

[malloc] unsorted bin unlink

[free] MINSIZE check

[free] invalid next size (fast)

[free] double free check

[free] invalid next size (normal)

[free] unsorted bin link

[realloc] unlink size vs. prev_size check

[realloc] invalid next size