Rewrite RGBLINK entirely

The goal was to improve readability, but along the way a few things were
gained.
- Sorted sym and map files
- Infrastructure for supporting multiple .o versions
- Valgrind-proof, as far as my testing goes anyways
- Improved verbosity messages
- Added error checking
- Performance improvements, see end of commit message

The readability improvement was spurred while trying to make sense of the
old code while trying to implement features such as sorted sym and map
files.
I also did my best to remove hardcoded logic, such that modifications
should be doable; for example, "RAM loading" sections, which are linked
against a different location than the one they're stored at.

Some work remains to be done, see the "TODO:" and "FIXME:" comments.
Further, while regression tests pass, this new linker should be tested on
different codebases (ideally while instrumented with `make develop` and
under valgrind).
The few errors spotted in the man pages (alignment) need to be corrected.
Finally, documentation comments need to be written, I have written a lot of
them but not all.

This also provides a significant performance boost (benchmarked with a
51994-symbol project):

Current master RGBLINK:
2.02user 0.03system 0:02.06elapsed 99%CPU (0avgtext+0avgdata 84336maxresident)k
0inputs+11584outputs (0major+20729minor)pagefaults 0swaps

Rewritten RGBLINK:
0.19user 0.06system 0:00.63elapsed 40%CPU (0avgtext+0avgdata 32460maxresident)k
23784inputs+11576outputs (0major+7672minor)pagefaults 0swaps

include/link/script.h

@@ -1,30 +1,34 @@
 /*
  * This file is part of RGBDS.
  *
- * Copyright (c) 2017-2018, Antonio Nino Diaz and RGBDS contributors.
+ * Copyright (c) 1997-2019, Carsten Sorensen and RGBDS contributors.
  *
  * SPDX-License-Identifier: MIT
  */
 
+/* Parsing a linker script */
 #ifndef RGBDS_LINK_SCRIPT_H
 #define RGBDS_LINK_SCRIPT_H
 
 #include <stdint.h>
 
-#include "helpers.h"
+struct SectionPlacement {
+	struct Section *section;
+	uint16_t org;
+	uint32_t bank;
+};
 
-noreturn_ void script_fatalerror(const char *fmt, ...);
+extern uint64_t script_lineNo;
 
-void script_Parse(const char *path);
+/**
+ * Parses the linker script to return the next section constraint
+ * @return A pointer to a struct, or NULL on EOF. The pointer shouldn't be freed
+ */
+struct SectionPlacement *script_NextSection(void);
 
-void script_IncludeFile(const char *path);
-int32_t script_IncludeDepthGet(void);
-void script_IncludePop(void);
-
-void script_InitSections(void);
-void script_SetCurrentSectionType(const char *type, uint32_t bank);
-void script_SetAddress(uint32_t addr);
-void script_SetAlignment(uint32_t alignment);
-void script_OutputSection(const char *section_name);
+/**
+ * `free`s all assignment memory that was allocated.
+ */
+void script_Cleanup(void);
 
 #endif /* RGBDS_LINK_SCRIPT_H */