Issue being fixed or feature implemented

This header gsl/pointers.h is included in multiple other headers all over codebase.
Any extra line of code inside gsl/pointers.h makes all project to compile slower.

What was done?

Removed headers <algorithm>, <system_error>, <iosfwd> from gsl/pointers.h

How Has This Been Tested?

Run command 5 times, takes minimum time:

• baseline

$ time g++ -o /tmp/a.out gsl/pointers.h -O2 -g -I.
real    0m0,572s
user    0m0,461s
sys     0m0,108s

• removed algorithm:

$ time g++ -o /tmp/a.out gsl/pointers.h -O2 -g -I.
real    0m0,505s
user    0m0,398s
sys     0m0,107s

• removed algorithm and system_error:

real    0m0,332s
user    0m0,265s
sys     0m0,067s

• disabled iostream:

$ time g++ -o /tmp/a.out gsl/pointers.h -O2 -g -I. -D GSL_NO_IOSTREAMS
real    0m0,316s
user    0m0,256s
sys     0m0,060s

as a result, overall project compilation time is also improved: make clean ; sleep 3s ; time make -j20

real    5m42,934s
user    80m35,127s
sys     6m40,735s

real    5m28,862s
user    75m31,931s
sys     6m32,591s

Breaking Changes

N/A

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have made corresponding changes to the documentation
• I have assigned this pull request to a milestone