Fix JFile to normalize whitespace when loading JSON from disk

JString::operator=(ZString) already stripped whitespace between JSON
structural tokens before parsing, but JFile constructed via MFile file-
loading bypassed that path entirely, so any pretty-printed/hand-edited
JSON file silently failed every locate()/exists()/get*() call. Widen
removeWhitespace() to protected and call it from JFile constructor.

JFile.cpp

@@ -15,8 +15,22 @@ namespace coreutils {
    // at offset 0 with no braces or separators at all). Detect that case
    // here and seed valid JSON explicitly.
    JFile::JFile(ZString filename) : MFile(filename) {
-      if(getLength() == 0)
+      if(getLength() == 0) {
 	*this << "{}";
+      } else {
+	 // MFile's own file-loading reads the raw bytes straight into the
+	 // shared MString buffer - it never goes through JString::operator=,
+	 // which is the only other place this class normally strips
+	 // whitespace before parsing (removeWhitespace()). Without this, a
+	 // JFile backed by a hand-written or pretty-printed JSON file (any
+	 // whitespace between tokens - indentation, newlines, spaces after
+	 // ':'/',') fails every locate()/exists()/get*() call, since
+	 // JString's parser expects compact JSON with no whitespace at all
+	 // between structural tokens. In-memory JSON built via operator=
+	 // never hit this because it already goes through the same
+	 // normalization - loading from disk just missed it.
+	 removeWhitespace();
+      }
    }