optimizes Scala reflection GIL

First of all, GIL should only apply to runtime reflection, because noone
is going to run toolboxes in multiple threads: a) that's impossible, b/c
the compiler isn't thread safe, b) ToolBox api prevents that.

Secondly, the only things in symbols which require synchronization are:
1) info/validTo (completers aren't thread-safe),
2) rawInfo and its dependencies (it shares a mutable field with info)
3) non-trivial caches like in typeAsMemberOfLock

If you think about it, other things like sourceModule or associatedFile
don't need synchronization, because they are either set up when a symbol
is created or cloned or when it's completed. The former is obviously safe,
while the latter is safe as well, because before acquiring init-dependent
state of symbols, the compiler calls `initialize`, which is synchronized.

We can say that symbols can be in four possible states: 1) being created,
2) created, but not yet initialized, 3) initializing, 4) initialized.
Of those only #3 is dangerous and needs protection, which is what this
commit does.

1 files changed, 0 insertions, 0 deletions

diff --git a/test/files/run/t6240-universe-code-gen.check b/test/files/run/t6240-universe-code-gen.check
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/test/files/run/t6240-universe-code-gen.check