have no other gods before c.h'.  Also remove some demonstrably redundant
#include lines, mostly of <errno.h> which was added to c.h years ago.

- Fix wrong index results on text, char, varchar for multibyte strings
- Fix some SIGFPE signals
- Add support for infinite timestamps
- Because of locale settings, btree_gist can not be a prefix index anymore (for text).
  Each node holds now just the lower and upper boundary.

methods in a short-lived memory context, there is no need for GiST methods
to do their own manual (and error-prone) memory management.

the "extern" keyword from function definitions, reorganize some
PG_GETARG_XXX() usage, and similar.

New version. Add support for int2, int8, float4, float8, timestamp with/without time zone, time with/without time zone, date, interval, oid, money and macaddr, char, varchar/text, bytea, numeric, bit, varbit, inet/cidr types for GiST