Fix for SPACK-35: Fortran not working properly

- Spack needed symlinks in env for fortran compilers.
- 'fc' is a bash bulitin, so can't use it for fortran compiler.
  - switched to 'f90' for this.

- mpich 3 builds with fortran now.
  - enabled shared libs in mpich package

lib/spack/env/cc

@@ -59,7 +59,7 @@ elif command in ('c++', 'CC', 'g++', 'clang++'):
 elif command in ('f77'):
     command = spack_f77
     language = "Fortran 77"
-elif command in ('fc'):
+elif command in ('fc', 'f90', 'f95'):
     command = spack_fc
     language = "Fortran 90"
 elif command in ('ld', 'cpp'):

lib/spack/env/f77

@@ -0,0 +1 @@
+cc

lib/spack/env/f90

@@ -0,0 +1 @@
+cc

lib/spack/env/f95

@@ -0,0 +1 @@
+cc

lib/spack/env/fc

@@ -0,0 +1 @@
+cc