This takes literal integers, not expressions, because each machine
defines its own valu_t for expressions, but valu_t can be too narrow
for an 8-byte integer, and I don't want to change all the machines to
use a wider valu_t. Instead, change how the assembler parses literal
integers. Remove the NUMBER token and add a NUMBER8 token for an
int64_t. The new .data8 pseudo emits all 8 bytes of the int64_t;
expressions narrow the int64_t to a valu_t. Don't add any checks for
integer overflow; expressions and .data* pseudos continue to ignore
overflow when a number is too wide.
This commit requires int64_t and uint64_t in the C compiler to build
the assembler. The ACK's own C compiler doesn't have these.
For the assembler's temporary file, add NUMBER4 to store 4-byte
integers. NUMBER4 acts like NUMBER[0-3] and only stores a
non-negative integer. Each negative integer now takes 8 bytes (up
from 4) in the temporary file.
Move the `\fI` and `\fP` in the uni_ass(6) manual, so the square
brackets in `thing [, thing]*` are not italic. This looks nicer in my
terminal, where italic text is underlined.
