Merge branch 'framework/add_gnu_implicit_none_flag' into develop (PR #1377)

This merge adds the -fimplicit-none flag to both the FFLAGS_OPT and FFLAGS_DEBUG
variables in the 'gnu' build target in the top-level Makefile. With the addition
of this flag, compilation will now fail with the gfortran compiler if implicitly
defined variables are present in Fortran source code.

* framework/add_gnu_implicit_none_flag:
  Add -fimplicit-none to FFLAGS_OPT and FFLAGS_DEBUG in 'gnu' build target

Author: mgduda

Makefile

@@ -16,11 +16,11 @@ gnu:   # BUILDTARGET GNU Fortran, C, and C++ compilers
 	"CC_SERIAL = gcc" \
 	"CXX_SERIAL = g++" \
 	"FFLAGS_PROMOTION = -fdefault-real-8 -fdefault-double-8" \
-	"FFLAGS_OPT = -std=f2008 -O3 -ffree-line-length-none -fconvert=big-endian -ffree-form" \
+	"FFLAGS_OPT = -std=f2008 -fimplicit-none -O3 -ffree-line-length-none -fconvert=big-endian -ffree-form" \
 	"CFLAGS_OPT = -O3" \
 	"CXXFLAGS_OPT = -O3" \
 	"LDFLAGS_OPT = -O3" \
-	"FFLAGS_DEBUG = -std=f2008 -g -ffree-line-length-none -fconvert=big-endian -ffree-form -fcheck=all -fbacktrace -ffpe-trap=invalid,zero,overflow" \
+	"FFLAGS_DEBUG = -std=f2008 -fimplicit-none -g -ffree-line-length-none -fconvert=big-endian -ffree-form -fcheck=all -fbacktrace -ffpe-trap=invalid,zero,overflow" \
 	"CFLAGS_DEBUG = -g" \
 	"CXXFLAGS_DEBUG = -g" \
 	"LDFLAGS_DEBUG = -g" \