Phase 7.9: multi-file build, module braces, struct init multi-line, else-if fix

_selfhost/src/source_location.bux

@@ -0,0 +1,13 @@
+// source_location.bux — Source position tracking
+module SourceLocation {
+
+struct SourceLocation {
+    line: uint32,
+    column: uint32,
+    offset: uint32,
+}
+
+func SourceLocation_New(line: uint32, column: uint32, offset: uint32) -> SourceLocation {
+    return SourceLocation { line: line, column: column, offset: offset };
+}
+}