Updated and added new functions related to headers, resolved ODR issues, resolved clang-tidy warnings (#50)

* Bugfix/odr violations (#47)

* Make common non-member functions inline, remove unreachable line from get_line_buffer

* [skip ci] Fix namespace comments

* Resolve clang-tidy warnings (#48)

* Resolve clang-tidy warnings, update single_header_generator.py

* Update single header test, resolve additional clang-tidy warnings

* Add header and raw_header methods,  update header usage methods error handling, write new and update existing unit tests

* Update parser error messages, fix parser tests

* Add [[nodiscard]] where fitting, update unit tests (#49)

* Add const where fitting, make splitter class members private, add #pragma once to ssp.hpp

* Modify header parsing for empty headers, update old and add new tests for header parsing

* Enable the parser to accept a header with one empty field, update unit tests

* Fix test CMakeLists.txt typo

test/meson.build

@@ -6,6 +6,7 @@ tests = [
   'parser1_2',
   'parser1_3',
   'parser1_4',
+  'parser1_5',
   'splitter',
   'converter',
   'extractions',