Add rb_intern2 and a stub for rb_intern3
Tests for rb_intern2 and rb_intern3
Tests for rb_intern3 are tagged in 1.9 and 2.0 modes
Merge pull request #2441 from sodabrew/rb_intern3

Stubs for rb_intern2 and rb_intern3
Fix missing header inclusion for symbol specs
Fixed installing with language mode changes.
More language mode cleanups.
Silence warnings compiling openssl C exts.
Added missing paths.h
Silence warnings compiling zlib C exts.
Removed generated C-API config in 2.0 mode.
Don't clean generated paths.h for now.
Generate C-API headers regardless of language mode.

We need eg oniguruma even in 1.8 mode because Encodings are used
(will be used) to implement 1.8 KCODE.
Add 2.0 C-API headers in ext_helper.
Remove unused rb_str Rubinius specific functions

rb_str_update() also collides with an actual Ruby C-API function, also
see #2459.
Add basic spec for rb_str_update
Add better inspect for Rubinius::Mirror
Add rb_str_update

Fixes #2459
Fix style of always using {}
Setup 1.9 aliases for rb_str_new4

In CRuby rb_str_new4 and rb_str_dup_frozen are aliases for
rb_str_new_frozen, but that would mean a bigger change since 1.8 mode
still uses the old non descriptive name rb_str_new4. So for now, we just
leave it at this.