Don't need to link with -ll or -ly.
ok millert@ (who spotted and provided the -ll removal bits)

Add -E flag (make warnings fatal), following the behavior of GNU m4 1.4.9+
Help and direction millert@ espie@ anton@ deraadt@

ok espie@

new m4 -g stuff:
- expr(`4**3')
- include(`hey I am not there') keeps going.

work with Baptiste Daroussin, who had the idea but didn't nail all details
right.

okay otto@, miod@

add more gnum4 support: regexps do weird things with empty patterns (this
is required for newer autoconf).
fix the tokenizer for gnu extensions, allowing digits out of range is
ridiculous.
add POSIX2008 mkstemp and document it (also documenting that mktemp is
safe, not posix...)
tidy the manpage, do extra .Nm m4 -> .Nm.
okay otto@, miod@, jmc@

gnu extension: 0rN:az for baseN numbers.

okay otto@

not yet, committed too much

argument parsing should only skip spaces outside of parenthesis.
Inside matching parenthesis, keep spaces as is (use chrsave instead of
pbstr, since there's no way it can be a further macro expansion).
Fixes a long-standing issue with autoconf ( --option -> --option),
matches other m4 than gnum4

okay millert@, fries@

use stdint.h where appropriate. okay millert@

all numbers as one composite regexp.

replace hand-made expr() parser with a lex/yacc affair that is shorter,
easier to understand and extend, and better conformant to Single Unix 3
(especially doing all arithmetic as int32_t).

Comments and approval millert@, otto@, fries@