Eliminate GCC 'missing initializer' warning for jcgo_globData

* include/jcgobase.c (jcgo_globData): Add missing jnull/NULL elements
to initialize all fields.
Samples: Add sample N3629 (for mingw-w32 4.8.0)
jtrsrc: VerInfo: update year to 2013
Use GCC __builtin_expect

* README (BUILTINEXPECTR): Document.
* include/jcgortl.h (BUILTINEXPECTR): New macro (for tuning); default
definition using GCC __builtin_expect.
* include/jcgortl.h (JCGO_EXPECT_FALSE, JCGO_EXPECT_TRUE): Define via
BUILTINEXPECTR (if present).
* jtrsrc/com/ivmaisoft/jcgo/Names.java (reservCNameArr): Add
BUILTINEXPECTR.