Suggest standard intrinsic functions when extensions are used

[Beliavsky]

Here is a list of gfortran extensions followed by their standard alternatives (which may have different semantics). Fortitude could suggest that non-standard intrinsics be replaced by standard ones. A lower priority would be to suggest replacement when possible for procedures in the ifport module of Intel Fortran https://www.intel.com/content/www/us/en/docs/fortran-compiler/developer-guide-reference/2024-2/portability-library-routines.html

Related issues:
#267
#282
#283

Fortran Discourse thread: https://fortran-lang.discourse.group/t/list-of-non-standard-intrinsic-functions-and-their-standard-alternatives/9107

system, execute_command_line

float, real

dfloat, dble or preferably replace dfloat(x) with real(x, kind=dp) with dp a double precision kind parameter

iargc, command_argument_count

getarg, get_command_argument

etime, system_clock (gfortran documentation says etime can be invoked as either a subroutine or function)

idate, date_and_time

itime, date_and_time

fdate, date_and_time

ctime, date_and_time

abort, stop

exit, stop

rand, random_number

srand, random_seed