Merge lit-unicode-*.inc.h-related generator scripts (#1767)

The `conversions` and `ranges` files had separate generators, which
shared some functionality through a 3rd python module, and were
quite similar to each other -- but also had some differences.
Moreover, as they were separate scripts, nothing forced to keep the
outputs in sync (to re-generate them at the same time from the same
inputs).

To fix these maintainability issues, this patch
- merges the two python files and part of the 3rd utility module
  into a single script while keeping the existing functionality,
- names the new file `gen-unicode.py` to align better with other
  generator script in `tools`, and
- adds some extra documentation how to retrieve the input files
  (as they are not part of the repository).

The refactoring affected the utility module as well, so this patch
also
- renames `c_source_helper.py` to `gen_c_source.py` (again, for
  naming consistency),
- reorganizes some of its functions not to export module-local
  helper functions, and
- adapts `js2c.py`, as it also uses this utility module.

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss akiss@inf.u-szeged.hu

tools/gen_c_source.py

@@ -0,0 +1,51 @@
+# Copyright JS Foundation and other contributors, http://js.foundation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+LICENSE = """/* Copyright JS Foundation and other contributors, http://js.foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */"""
+
+
+def format_code(code, indent, digit_number=4):
+    def regroup(list_to_group, num):
+        return [list_to_group[i:i+num] for i in range(0, len(list_to_group), num)]
+
+    def hex_format(char, digit_number):
+        if isinstance(char, str):
+            char = ord(char)
+
+        return ("0x{:0%sx}" % digit_number).format(char)
+
+    lines = []
+
+    nums_per_line = 10
+    width = nums_per_line * (digit_number + 4)
+    # convert all characters to hex format
+    converted_code = [hex_format(char, digit_number) for char in code]
+    # 10 hex number per line
+    for line in regroup(", ".join(converted_code), width):
+        lines.append(('  ' * indent) + line.strip())
+    return "\n".join(lines)