Add arguments to C macros that need them. (#724)

* Add arguments to C macros that need them.

Previously no macros took arguments, even those that depended on e.g.
XLEN.

Old:
 #define CSR_TDATA1_TYPE_OFFSET              (XLEN-4)
 #define CSR_TDATA1_TYPE_LENGTH              4
 #define CSR_TDATA1_TYPE                     (0xfULL << CSR_TDATA1_TYPE_OFFSET)

New:
 #define CSR_TDATA1_TYPE_OFFSET(XLEN)        (XLEN + -4)
 #define CSR_TDATA1_TYPE_LENGTH              4
 #define CSR_TDATA1_TYPE(XLEN)               (0xf * (1ULL<<(XLEN + -4)))

The new syntax can be a little awkward, but it's correct and works in
OpenOCD at least. The most awkward new version is this one:
 #define DTM_DMI_ADDRESS_OFFSET              0x22
 #define DTM_DMI_ADDRESS_LENGTH(abits)       abits
 #define DTM_DMI_ADDRESS(abits)              ((0x400000000ULL * (1ULL<<abits)) + -17179869184)

Some of the awkwardness stems from the fact that sympy doesn't support a
<< operator, so I use ** internally and then print it out strangely.
It's correct, just not idiomatic.

* Tweak how we represent numbers.

Add appropriate U and ULL prefix on large hex constants that we negate.