Use pacsort instead of sort for the package index

 pacsort is required to list packages in the right order.

 Example: `agetpkg  -l '^linux$' |tail`

 Before:
 linux 4.3.2-1 x86_64
 linux 4.3.3-1 x86_64
 linux 4.3.3-2 x86_64
 linux 4.3.3-3 x86_64
 linux 4.4.1-1 x86_64
 linux 4.4.1-2 x86_64
 linux 4.4-1 x86_64
 linux 4.4-2 x86_64
 linux 4.4-3 x86_64
 linux 4.4-4 x86_64

 After:
 linux 4.3.2-1 x86_64
 linux 4.3.3-1 x86_64
 linux 4.3.3-2 x86_64
 linux 4.3.3-3 x86_64
 linux 4.4-1 x86_64
 linux 4.4-2 x86_64
 linux 4.4-3 x86_64
 linux 4.4-4 x86_64
 linux 4.4.1-1 x86_64
 linux 4.4.1-2 x86_64

Signed-off-by: Mohammad AlSaleh <CE.Mohammad.AlSaleh@gmail.com>