initial OpenBSD support

core/c/libc/errno.odin

@@ -27,6 +27,19 @@ when ODIN_OS == .Linux || ODIN_OS == .FreeBSD {
 	ERANGE :: 34
 }
 
+when ODIN_OS == .OpenBSD {
+	@(private="file")
+	@(default_calling_convention="c")
+	foreign libc {
+		@(link_name="__errno")
+		_get_errno :: proc() -> ^int ---
+	}
+
+	EDOM   :: 33
+	EILSEQ :: 84
+	ERANGE :: 34
+}
+
 when ODIN_OS == .Windows {
 	@(private="file")
 	@(default_calling_convention="c")

core/c/libc/stdio.odin

@@ -78,6 +78,31 @@ when ODIN_OS == .Linux {
 	}
 }
 
+when ODIN_OS == .OpenBSD {
+	fpos_t :: i64
+
+	_IOFBF :: 0
+	_IOLBF :: 1
+	_IONBF :: 1
+
+	BUFSIZ :: 1024
+
+	EOF :: int(-1)
+
+	FOPEN_MAX	:: 20
+	FILENAME_MAX	:: 1024
+
+	SEEK_SET :: 0
+	SEEK_CUR :: 1
+	SEEK_END :: 2
+
+	foreign libc {
+		stderr: ^FILE
+		stdin:  ^FILE
+		stdout: ^FILE
+	}
+}
+
 when ODIN_OS == .Darwin {
 	fpos_t :: distinct i64
 	

core/c/libc/time.odin

@@ -45,7 +45,7 @@ when ODIN_OS == .Windows {
 	}
 }
 
-when ODIN_OS == .Linux || ODIN_OS == .FreeBSD || ODIN_OS == .Darwin {
+when ODIN_OS == .Linux || ODIN_OS == .FreeBSD || ODIN_OS == .Darwin || ODIN_OS == .OpenBSD {
 	@(default_calling_convention="c")
 	foreign libc {
 		// 7.27.2 Time manipulation functions
@@ -63,7 +63,12 @@ when ODIN_OS == .Linux || ODIN_OS == .FreeBSD || ODIN_OS == .Darwin {
 		strftime     :: proc(s: [^]char, maxsize: size_t, format: cstring, timeptr: ^tm) -> size_t ---
 	}
 
-	CLOCKS_PER_SEC :: 1000000
+	when ODIN_OS == .OpenBSD {
+		CLOCKS_PER_SEC :: 100
+	} else {
+		CLOCKS_PER_SEC :: 1000000
+	}
+
 	TIME_UTC       :: 1
 
 	time_t         :: distinct i64

core/c/libc/wctype.odin

@@ -25,6 +25,11 @@ when ODIN_OS == .Darwin {
 	wctype_t  :: distinct u32
 }
 
+when ODIN_OS == .OpenBSD {
+	wctrans_t :: distinct rawptr
+	wctype_t  :: distinct rawptr
+}
+
 @(default_calling_convention="c")
 foreign libc {
 	// 7.30.2.1 Wide character classification functions