Byte compilation should be separately done for each file

[stephan-cr]

$ byte-compile -Werror *.el

... nothing.

$ for i in *.el ; do byte-compile -Werror $i ; done

In toplevel form:
el-get-byte-compile.el:64:9:Error: reference to free variable ‘el-get-byte-compile’

In toplevel form:
el-get-core.el:42:9:Error: reference to free variable ‘el-get-verbose’

In toplevel form:
el-get-dependencies.el:186:1:Error: the function ‘el-get-read-package-with-status’ is not known to be defined.

In toplevel form:
el-get.el:199:28:Error: The compiler ignores ‘autoload’ except at top level.  You should
     probably put the autoload of the macro ‘el-get-bundle’ at top-level.

In toplevel form:
el-get-list-packages.el:452:1:Error: the following functions are not known to be defined: el-get-recipe-filename, el-get-package-type, el-get-package-def, el-get-package-method, el-get-version-to-list, el-get-recipe-pprint, el-get-read-all-recipes

In toplevel form:
el-get-methods.el:46:11:Error: reference to free variable ‘el-get-allow-insecure’

In toplevel form:
el-get-recipes.el:331:1:Error: the function ‘el-get-github-parse-user-and-repo’ is not known to be defined.

In toplevel form:
el-get-status.el:81:21:Error: reference to free variable ‘el-get-status-file’

This issue causes spurious CI failures.