gdb: Use initializers in lambda captures unconditionally

Initializer in lambda captures were introduced in C++14, and
conditionally used in gdb/cp-support.c and gdb/dwarf2/cooked-index.c.

Since C++17 is now required by GDB, use this feature unconditionally.

Change-Id: I87a3d567941e5c71217538fa75c952e4d421fa1d
2 files changed