fixes loading unit tests with "main" as the entry point.

The glibc headers define those as macros, need to undefine before declaring
as functions.

Found with mode=release.

A mutex will also call wait_until, which doesn't tolerate nesting.

Fail the build if not.

Needed by bench.jar suddenly.

Running tests is now done by editing the command line in build.mak

This makes it easy to configure a thread with various parameters.  The first
is the existing stack_info parameter.

Of course we don't actually support locales yet, so these are trivial wrappers.

This ones handles the current working directory in relative pathnames,
and supports the POSIX.1-2008 case where the resolved_path argument is
passed a NULL and then allocated by realpath internally.

current_pthread was somehow not thread-local, so pthread_self() returned
the last thread to initialize itself.  The bug manifested itself with
a jvm thread querying its own stack, finding another thread's stack instead,
and reaching the conclusion that it was in a stack overflow, and throwing
an exception.

Fix by making current_pthread thread local.

We need to use a spinlock to protect the semaphore waiting list as
the wakeups can deadlock otherwise.

Also make sure to only wait when we actually have to.

Found during python bringup.

no actual checking, but at least the code will work

again taken from musl.

For now disabled:

 - floor, ceil: we have an asm implementation, but need to check if it's enough
 - various functions that mess with the floating point exception status.

The payload is likely to play games with the stack area (like mmap()ing guard
pages), so give it virtual memory to play with instead of physical memory.

Fixes crash with mode=release.

glibc headers define various standard functions as macros, which breaks
the build.  #undef them in the source files.

We want these in line buffered mode, but to get that we need to query the
console driver if it is a tty, and we can only do that after the VFS has
been brought up.

except for the floating point functionality for now.