Move version files out of extern folder

The folder extern is reserved for external contributions, not common
files.

Signed-off-by: Antonio Niño Díaz <antonio_nd@outlook.com>

Makefile

@@ -58,7 +58,7 @@ rgbasm_obj := \
 	src/asm/symbol.o \
 	src/extern/err.o \
 	src/extern/utf8decoder.o \
-	src/extern/version.o
+	src/version.o
 
 src/asm/asmy.h: src/asm/asmy.c
 src/asm/locallex.o src/asm/globlex.o src/asm/lexer.o: src/asm/asmy.h
@@ -76,7 +76,7 @@ rgblink_obj := \
 	src/link/script.o \
 	src/link/symbol.o \
 	src/extern/err.o \
-	src/extern/version.o
+	src/version.o
 
 src/link/parser.h: src/link/parser.c
 src/link/lexer.o: src/link/parser.h
@@ -84,14 +84,14 @@ src/link/lexer.o: src/link/parser.h
 rgbfix_obj := \
 	src/fix/main.o \
 	src/extern/err.o \
-	src/extern/version.o
+	src/version.o
 
 rgbgfx_obj := \
 	src/gfx/gb.o \
 	src/gfx/main.o \
 	src/gfx/makepng.o \
 	src/extern/err.o \
-	src/extern/version.o
+	src/version.o
 
 rgbasm: ${rgbasm_obj}
 	$Q${CC} ${REALCFLAGS} -o $@ ${rgbasm_obj} -lm

src/asm/main.c

@@ -22,7 +22,8 @@
 #include "asm/main.h"
 
 #include "extern/err.h"
-#include "extern/version.h"
+
+#include "version.h"
 
 extern int yyparse(void);
 

src/asm/symbol.c

@@ -24,7 +24,8 @@
 #include "asm/output.h"
 
 #include "extern/err.h"
-#include "extern/version.h"
+
+#include "version.h"
 
 struct sSymbol *tHashedSymbols[HASHSIZE];
 static struct sSymbol *pScope; /* Current section symbol scope */

src/fix/main.c

@@ -14,7 +14,8 @@
 #include <unistd.h>
 
 #include "extern/err.h"
-#include "extern/version.h"
+
+#include "version.h"
 
 static void print_usage(void)
 {

src/gfx/main.c

@@ -10,10 +10,10 @@
 #include <string.h>
 #include <unistd.h>
 
-#include "extern/version.h"
-
 #include "gfx/main.h"
 
+#include "version.h"
+
 static void print_usage(void)
 {
 	printf(

src/link/main.c

@@ -13,7 +13,6 @@
 #include <unistd.h>
 
 #include "extern/err.h"
-#include "extern/version.h"
 
 #include "link/object.h"
 #include "link/output.h"
@@ -24,6 +23,8 @@
 #include "link/main.h"
 #include "link/library.h"
 
+#include "version.h"
+
 enum eBlockType {
 	BLOCK_COMMENT,
 	BLOCK_OBJECTS,

src/version.c

@@ -9,7 +9,7 @@
 #include <stdio.h>
 #include <string.h>
 
-#include "extern/version.h"
+#include "version.h"
 
 const char *get_package_version_string(void)
 {