implement "low hanging fruit" from C11

based on Gregor's patch sent to the list. includes:
- stdalign.h
- removing gets in C11 mode
- adding aligned_alloc and adjusting other functions to use it
- adding 'x' flag to fopen for exclusive mode

include/stdalign.h

@@ -0,0 +1,15 @@
+#ifndef _STDALIGN_H
+#define _STDALIGN_H
+
+/* this whole header only works in C11 or with compiler extensions */
+#if __STDC_VERSION__ < 201112L && defined( __GNUC__)
+#define _Alignas(t) __attribute__((__aligned__(t)))
+#define _Alignof(t) __alignof__(t)
+#endif
+
+#define alignas _Alignas
+#define alignof _Alignof
+#define __alignas_is_defined 1
+#define __alignof_is_defined 1
+
+#endif

include/stdio.h

@@ -90,7 +90,9 @@ int putc(int, FILE *);
 int putchar(int);
 
 char *fgets(char *, int, FILE *);
+#if __STDC_VERSION__ < 201112L
 char *gets(char *);
+#endif
 
 int fputs(const char *, FILE *);
 int puts(const char *);

include/stdlib.h

@@ -38,6 +38,7 @@ void *malloc (size_t);
 void *calloc (size_t, size_t);
 void *realloc (void *, size_t);
 void free (void *);
+void *aligned_alloc(size_t alignment, size_t size);
 
 void abort (void);
 int atexit (void (*) (void));