<NME> string_format_many_replace.ly
<BEF> ADDFILE
<MSG> Finally implement string::format (Fixes #34).

This ended up being simpler than expected to do. A couple of tests
have also been added to make sure string::format doesn't decide to
break.

I've tested this implementation under valgrind to look for invalid
reads and found none (surprising, since the majority of this was done
at 2AM).

<DFF> @@ -0,0 +1,6 @@
+# Make sure string::format can handle multiple formats by each other.
+
+var s: string = "    "
+var result = string::format("%s%s%s%s%s%s%s%s%s%s", s,s,s,s,s,s,s,s,s,s)
+if result != "                                        ":
+    print("Failed.\n")

{'addition_count': 6, 'commit_subject': 'Finally implement string::format (Fixes #34).', 'deletion_count': 0, 'file_extension': '.ly', 'lang': 'ly', 'license': 'mit', 'repo_name': 'FascinatedBox/lily'}