Fix broken links

Author: chrisseaton

bench/chunky_png/README.md

@@ -1,5 +1,4 @@
-These benchmarks are originally from
-[Bench 9000](https://github.com/jruby/bench9000).
+These benchmarks are originally from JRuby Bench 9000.
 
 We are using ChunkyPNG at revision `efd61c8d0ddcabdcf09fb44f8e8c1ba709995940`.
 We use this old revision because we know it has interesting patterns of

bench/psd.rb/README.md

@@ -1,5 +1,4 @@
-These benchmarks are originally from
-[Bench 9000](https://github.com/jruby/bench9000).
+These benchmarks are originally from JRuby Bench 9000.
 
 We are using PSD.rb at revision `e14d652ddc705e865d8b2b897d618b25d78bcc7c`.
 We use this old revision because we know it has interesting patterns of

doc/contributor/third-party-assumptions.md

@@ -1,7 +1,7 @@
 # Assumptions Third Party Code Makes About TruffleRuby
 
 Third-party code should never use any APIs apart from standard Ruby, and those
-listed in [TruffleRuby additions]('../user/truffleruby-additions.md').
+listed in [TruffleRuby additions](../user/truffleruby-additions.md).
 
 When third-party code uses the TruffleRuby additions, it should be listed here
 so that we know why non-standard APIs have been added.

doc/user/jruby-migration.md

@@ -13,9 +13,9 @@ If you don't need the Java interop capabilities of TruffleRuby then you could
 also install via your [Ruby manager/installer](ruby-managers.md)
 as any other implementation of Ruby.
 
-You can also use the
-[standalone distribution](doc/user/standalone-distribution.md) as a simple
-binary tarball. The binary tarball also doesn't allow for Java interop.
+You can also use the [standalone distribution](standalone-distribution.md) as
+a simple binary tarball. The binary tarball also doesn't allow for Java
+interop.
 
 ## Using Ruby from Java