c574bd33c39d91c487c3fcd819226ecfc46c13c8

Several people have requested that the assert macros in EUnit should be
moved out to a separate header file. This patch puts them in
stdlib/include/assert.hrl, which gets included by the eunit.hrl file.
Thus, nothing changes for eunit users, but the asserts can now also be
included separately.

This reverts commit e56cf8d9846e51ae88fa72c8b0992d81da6fd7d5.

A convenience macro used for testing message passing logic by allowing
to fail if a message matching a `Guard` is not received in the mailbox
of the current process.

All output from eunit is unicode, including the surefire XML files.

This makes typos such as missing commas between two assertions
(e.g. ?assert(true) ?assert(true)) syntax errors instead of silently
compiling and failing with a badfun error at runtime.

This won't break any existing code as parenthesed expressions and blocks
have the same precedence and none of these macros can be used as patterns.