make __func__ a special static local

The __func__ static local variable should be deemed "special", because
it doesn't need to be correlated and should be included when needed by
an include function.

I don't have a test case for F20, but this fixes the following types of
issues when doing a full-tree recompile on RHEL 7:

    ERROR: cifssmb.o: object size mismatch: __func__.49322
    ERROR: btmrvl_main.o: kpatch_correlate_static_local_variables: 982: static local variable __func__.44657 not used
    ERROR: iwch_qp.o: .rodata.__func__.46024 section header details differ
allow static locals to be used by two functions

Allow static locals to be used by two functions.  This is possible if
the static's containing function is inlined.  We only need to find one
of them to do the correlation.
Merge pull request #443 from jpoimboe/func-special-static

static local fixes