Add full compiler toolchain, libc, examples and reference docs

First substantive commit: the entire Sprinter C compiler tree on top of
the bare README+gitignore initial commit.

What's in here:
  bin/sprinter-cc        — driver script invoking SDCC + linker + mkexe
  libc/                  — Sprinter-specific libc layer over ESTEX/BIOS
                           (conio, gfx, io, mem, stdio + headers)
  runtime/               — crt0 variants (default/small/banked/minimal)
                           + heap + bank trampolines
  toolchain/             — mkexe (SprintEXE packer, C + tests)
  examples/              — 30 demo programs (gfx, file I/O, env, time, …)
  lib/Makefile           — builds the libc archive (sprinter.lib)
  docs/                  — converted Sprinter manuals + asm reference samples
  third_party/           — solid-c reference compiler dump + sdcc setup script
  release_docs/          — packaging / release notes

gitignore overhaul:
  • Drop dangerous blanket patterns: *.asm (would hide docs/samples/*.asm)
    and *.exe (case-insensitive match was hiding third_party/solid-c/*.EXE
    on macOS APFS).  Replaced with examples/*/*.{asm,exe,…} and lib/*.lib.
  • Restore tracking of toolchain/mkexe/tests/{one,big}.bin — those are
    INPUT fixtures, not build outputs.
  • Collapse the duplicated SDCC/C/Sdcc sections into one section per
    concern (build outputs / vendored / OS-junk).
  • Add .sprinter-cc-*/, build/ (catches lib/build/ too), .claude/.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

third_party/solid-c/INCLUDE/STDIO.H

@@ -0,0 +1,117 @@
+/*
+ *	STDIO.H
+ *
+ *      Definitions for stream input/output.
+ *	(c) 2004, SOLID C  Sprinter-2000
+ */
+
+
+#ifndef	_C_TYPES_
+#include <types.h>
+#endif
+
+#ifndef	_STD_LIB_
+#include <stdlib.h>
+#endif
+
+
+
+/* definition of the control structure for streams */
+typedef	struct {
+	uint flags;		/* +0,1  file status flags		*/
+	int  level;		/* +2,3  empty/fill level of buffer	*/
+	char *curp;		/* +4,5  current active pointer		*/
+	int  fd;		/* +6,7  file descriptor for low-level i/o */
+	char *buffer;		/* +8,9  addr data transfer buffer	*/
+	char hold;		/* +10   ungetc char if no buffer	*/
+	short token;		/* +11,12 reserved			*/
+	char dummy;		/* +13   reserved			*/
+} FILE;		/* this is the FILE object */
+
+
+/* "flags" bits definitions */
+#define _F_READ  0x0001			/* 0  read only file		*/
+#define _F_WRIT  0x0002			/* 1  write only file		*/
+#define _F_RDWR  0x0003			/* 0,1 read/write flag		*/
+#define _F_BUF   0x0004			/* 2  malloc'ed Buffer data	*/
+#define _F_LBUF  0x0008			/* 3  line-buffered file	*/
+#define _F_ERR   0x0010			/* 4  error indicator		*/
+#define _F_EOF   0x0020			/* 5  EOF indicator		*/
+#define _F_BIN   0x0040			/* 6  binary file indicator	*/
+#define _F_IN    0x0080			/* 7  data is incoming		*/
+#define _F_OUT   0x0100			/* 0 +1  data is outgoing	*/
+#define _F_TERM  0x0200			/* 1 +1  stdin stream		*/
+
+
+#define	EOF	(-1)			/* end of file indicator */
+
+#define	BUFSIZ	512			/* buffer size for high-level i/o */
+
+#define	OPEN_MAX  8			/* able to have 8 files */
+
+extern FILE  _iob[];			/* list of fcb */
+
+/* standard I/O predefined streams */
+#define	stdin	(&_iob[0])
+#define	stdout	(&_iob[-1])
+#define	stderr	(&_iob[-2])
+#define	stdaux	(&_iob[-3])
+#define	stdprn	(&_iob[-4])
+
+
+/* for fgetpos, fsetpos functions */
+typedef	long fpos_t;		/* file offset type */
+
+
+#ifndef	_STD_SEEK_
+#define	_STD_SEEK_
+/* constants to be used as 3rd argument for "fseek" function */
+#define	SEEK_SET	0
+#define	SEEK_CUR	1
+#define	SEEK_END	2
+#endif
+
+
+/* Prototypes */
+
+int printf(.);
+int fprintf(.);
+int sprintf(.);
+int scanf(.);
+int sscanf(.);
+int fscanf(.);
+void clearerr();
+FILE *fdopen();
+FILE *fopen();
+FILE *freopen();
+void fclosall();
+char fclose();
+size_t fread();
+size_t fwrite();
+struct fpoint *fseek();
+struct fpoint *ftell();
+
+char getc();
+char putc();
+char *gets();
+char puts();
+char *fgets();
+char fputs();
+char fgetc();
+char fputc();
+char ungetc();
+char fflush();
+void rewind();
+char fgetpos();
+char fsetpos();
+
+
+
+/* The following macros provide for common functions */
+
+#define	fileno(a)	((a)->fd)
+#define	ferror(a)	((a)->flags & _F_ERR)
+#define	feof(a)		((a)->flags & _F_EOF)
+
+#define	fgetchar	getc(stdin)
+#define	fputchar(c)	putc((c),stdout)