allow multiple references to same static local var

This fixes a logic bug in the static local variable code where we don't
allow multiple relocation references to the same static local variable
symbol.
support renaming of unbundled static locals

WARN_ON_ONCE places the __warned static local variable in the
.data.unlikely section, so it's not bundled (i.e. ignored by the
-fdata-sections gcc flag).  There's no reason why we can't rename
unbundled symbols, so add support for them.

Fixes #394.
add test case for issue #394.
code review fixes

Rename bundled1 to bundled and bundled2 to basebundled.
Merge pull request #395 from jpoimboe/static-local-fixes

static local variable fixes for WARN_ON_ONCE