Fix bug in count_if() and find_if() with Intel CPUs

This fixes a bug in which the Intel OpenCL compiler would
fail to compile the count_if() and find_if() kernels for
vector types with the following error:

error: no matching function for call to 'all'
note: candidate function not viable: 1st argument ('__global int4')
is in address space 16776960, but parameter must be in address space 0

This is caused when the predicate compares a value from the input
buffer (in the global memory space) to a literal value (in the
private memory space).

This is fixed by first reading the value into a local variable in
the private memory space and then calling the predicate function.
Fix bug in remove_if() algorithm

This fixes a bug in which the remove_if() function would overwrite
parts of the input before they were properly copied to the output
range. This is fixed by first copying the input values to a temporary
vector and then passing that as the input range to copy_if().