refactor(api): Thread and log API

Split files and add name spacing.

src/api/log.h

@@ -0,0 +1,31 @@
+#ifndef BEMANITOOLS_API_THREAD_H
+#define BEMANITOOLS_API_THREAD_H
+
+#include <stdint.h>
+
+#ifdef __GNUC__
+/* Bemanitools is compiled with GCC (MinGW, specifically) as of version 5 */
+#define LOG_CHECK_FMT __attribute__((format(printf, 2, 3)))
+#else
+/* Compile it out for MSVC plebs */
+#define LOG_CHECK_FMT
+#endif
+
+/* An AVS-style logger function. Comes in four flavors: misc, info, warning,
+   and fatal, with increasing severity. Fatal loggers do not return, they
+   abort the running process after writing their message to the log.
+
+   "module" is an arbitrary short string identifying the source of the log
+   message. The name of the calling DLL is a good default choice for this
+   string, although you might want to identify a module within your DLL here
+   instead.
+
+   "fmt" is a printf-style format string. Depending on the context in which
+   your DLL is running you might end up calling a logger function exported
+   from libavs, which has its own printf implementation (including a number of
+   proprietary extensions), so don't use any overly exotic formats. */
+
+typedef void (*btapi_log_formatter_t)(const char *module, const char *fmt, ...)
+    LOG_CHECK_FMT;
+
+#endif

src/api/thread.h

@@ -0,0 +1,20 @@
+#ifndef BEMANITOOLS_API_THREAD_H
+#define BEMANITOOLS_API_THREAD_H
+
+#include <stdint.h>
+
+/* An API for spawning threads. This API is defined by libavs, although
+   Bemanitools itself may supply compatible implementations of these functions
+   to your DLL, depending on the context in which it runs.
+
+   NOTE: You may only use the logging functions from a thread where Bemanitools
+   calls you, or a thread that you create using this API. Failure to observe
+   this restriction will cause the process to crash. This is a limitation of
+   libavs itself, not Bemanitools. */
+
+typedef int (*btapi_thread_create_t)(
+    int (*proc)(void *), void *ctx, uint32_t stack_sz, unsigned int priority);
+typedef void (*btapi_thread_join_t)(int thread_id, int *result);
+typedef void (*btapi_thread_destroy_t)(int thread_id);
+
+#endif