Changes in derived_rb_evaluation.C for -Wshadow.

Issue #24.
Changes in derived_rb_construction.C for -Wshadow.

Issue #24.
Changes in fem_function_base.h for -Wshadow.

Issue #24.
Changes in rb_construction.C for -Wshadow.

Issue #24.
Changes in rb_construction_base.C for -Wshadow.

Issue #24.
Changes in rb_evaluation.C for -Wshadow.

Issue #24.
Changes in rb_eim_construction.C for -Wshadow.

Issue #24.
Changes in transient_rb_evaluation.C for -Wshadow.

Issue #24.
Changes in transient_rb_construction.C for -Wshadow.

Issue #24.
Changes in nanoflann.hpp for -Wshadow.

Issue #24.