Fix some issues with Makefiles mentioned in #294

[jvdp1]

Fixing the following issues related to Makefiles mentioned in #294:

• Generated .f90 files by fypp can now be cleaned with the clean rule
• Dependency added for common.fypp

[awvwgk]

Looks good to me. Just be wary with the out-of-order declaration of SRCGEN, which is valid in make but might be unexpected/surprising for people not familiar with the make evaluation logic.

[milancurcic]

I tested it and it works. Actually, this also seems to fix the manual Makefile build for some source files which appear to not have been included in the build in #294 (now in master):

$ du stdlib/src/libstdlib.a 
17664	stdlib/src/libstdlib.a
$ nm stdlib/src/libstdlib.a | wc -l
2102
$ ls stdlib/src/*o
stdlib/src/f18estop.o              stdlib/src/stdlib_kinds.o             stdlib/src/stdlib_stats_mean.o
stdlib/src/stdlib_ascii.o          stdlib/src/stdlib_linalg_diag.o       stdlib/src/stdlib_stats_moment_all.o
stdlib/src/stdlib_bitsets_64.o     stdlib/src/stdlib_linalg.o            stdlib/src/stdlib_stats_moment_mask.o
stdlib/src/stdlib_bitsets_large.o  stdlib/src/stdlib_logger.o            stdlib/src/stdlib_stats_moment.o
stdlib/src/stdlib_bitsets.o        stdlib/src/stdlib_optval.o            stdlib/src/stdlib_stats_moment_scalar.o
stdlib/src/stdlib_error.o          stdlib/src/stdlib_quadrature.o        stdlib/src/stdlib_stats.o
stdlib/src/stdlib_io.o             stdlib/src/stdlib_quadrature_trapz.o  stdlib/src/stdlib_stats_var.o
$ ls stdlib/src/*o
stdlib/src/f18estop.o              stdlib/src/stdlib_kinds.o             stdlib/src/stdlib_stats_mean.o
stdlib/src/stdlib_ascii.o          stdlib/src/stdlib_linalg_diag.o       stdlib/src/stdlib_stats_moment_all.o
stdlib/src/stdlib_bitsets_64.o     stdlib/src/stdlib_linalg.o            stdlib/src/stdlib_stats_moment_mask.o
stdlib/src/stdlib_bitsets_large.o  stdlib/src/stdlib_logger.o            stdlib/src/stdlib_stats_moment.o
stdlib/src/stdlib_bitsets.o        stdlib/src/stdlib_optval.o            stdlib/src/stdlib_stats_moment_scalar.o
stdlib/src/stdlib_error.o          stdlib/src/stdlib_quadrature.o        stdlib/src/stdlib_stats.o
stdlib/src/stdlib_io.o             stdlib/src/stdlib_quadrature_trapz.o  stdlib/src/stdlib_stats_var.o
$ du stdlib_jvdp1/src/libstdlib.a 
19652	stdlib_jvdp1/src/libstdlib.a
$ nm stdlib_jvdp1/src/libstdlib.a | wc -l
2493
$ ls stdlib_jvdp1/src/*o
stdlib_jvdp1/src/f18estop.o              stdlib_jvdp1/src/stdlib_linalg_diag.o       stdlib_jvdp1/src/stdlib_stats_cov.o
stdlib_jvdp1/src/stdlib_ascii.o          stdlib_jvdp1/src/stdlib_linalg.o            stdlib_jvdp1/src/stdlib_stats_mean.o
stdlib_jvdp1/src/stdlib_bitsets_64.o     stdlib_jvdp1/src/stdlib_logger.o            stdlib_jvdp1/src/stdlib_stats_moment_all.o
stdlib_jvdp1/src/stdlib_bitsets_large.o  stdlib_jvdp1/src/stdlib_optval.o            stdlib_jvdp1/src/stdlib_stats_moment_mask.o
stdlib_jvdp1/src/stdlib_bitsets.o        stdlib_jvdp1/src/stdlib_quadrature.o        stdlib_jvdp1/src/stdlib_stats_moment.o
stdlib_jvdp1/src/stdlib_error.o          stdlib_jvdp1/src/stdlib_quadrature_simps.o  stdlib_jvdp1/src/stdlib_stats_moment_scalar.o
stdlib_jvdp1/src/stdlib_io.o             stdlib_jvdp1/src/stdlib_quadrature_trapz.o  stdlib_jvdp1/src/stdlib_stats.o
stdlib_jvdp1/src/stdlib_kinds.o          stdlib_jvdp1/src/stdlib_stats_corr.o        stdlib_jvdp1/src/stdlib_stats_var.o

[milancurcic]

Thanks @jvdp1, I will merge.