Add support for 64-bit memory reads/writes (#419)

* 64-bit progbuf memory reads work.

Change-Id: Ia3dbc0ee39a31ed0e5c38bbb3d9e089b2533f399

* 64-bit writes work.

Change-Id: Iae78711d715b6682817bb7cce366b0094bda8b23

* Let targets indicate number of supported data bits.

This is used by the default memory read/write functions when creating an
aligned block.

I'm adding this mainly to ensure I get coverage of the 64-bit progbuf
memory read/write code.

Change-Id: Ie5909fe537c9ec3360a8d2837f84be00a63de77b

* Make mingw32 happy.

Change-Id: Iade8c1fdfc72ccafc82f2f34923577032b668916

src/target/riscv/program.c

@@ -79,6 +79,11 @@ int riscv_program_exec(struct riscv_program *p, struct target *t)
 	return ERROR_OK;
 }
 
+int riscv_program_sdr(struct riscv_program *p, enum gdb_regno d, enum gdb_regno b, int offset)
+{
+	return riscv_program_insert(p, sd(d, b, offset));
+}
+
 int riscv_program_swr(struct riscv_program *p, enum gdb_regno d, enum gdb_regno b, int offset)
 {
 	return riscv_program_insert(p, sw(d, b, offset));
@@ -94,6 +99,11 @@ int riscv_program_sbr(struct riscv_program *p, enum gdb_regno d, enum gdb_regno
 	return riscv_program_insert(p, sb(d, b, offset));
 }
 
+int riscv_program_ldr(struct riscv_program *p, enum gdb_regno d, enum gdb_regno b, int offset)
+{
+	return riscv_program_insert(p, ld(d, b, offset));
+}
+
 int riscv_program_lwr(struct riscv_program *p, enum gdb_regno d, enum gdb_regno b, int offset)
 {
 	return riscv_program_insert(p, lw(d, b, offset));