New Configure options "threads" and "no-threads".

For Solaris and Linux, "threads" (with proper compiler options)
is the default.
Submitted by:
Reviewed by:
PR:

INSTALL

@@ -37,6 +37,13 @@
 
   rsaref        Build with RSADSI's RSAREF toolkit.
 
+  no-threads    Don't try to build with support for multi-threaded
+                applications.
+
+  threads       Build with support for multi-threaded applications.
+                This will usually require additional system-dependent options!
+                See "Note on multi-threading" below.
+
   no-asm        Build with no assembler code.
 
   386           Use the 80386 instruction set only (the default x86 code is
@@ -180,6 +187,22 @@
      with names of the form <foo.h>.
 
 
+ Note on multi-threading
+ -----------------------
+
+ For some systems, the OpenSSL Configure script knows what compiler options
+ are needed to generate a library that is suitable for multi-threaded
+ applications.  On these systems, support for multi-threading is enabled
+ by default; use the "no-threads" option to disable (this should never be
+ necessary).
+
+ On other systems, to enable support for multi-threading, you will have
+ to specifiy at least two options: "threads", and a system-dependent option.
+ (The latter is "-D_REENTRANT" on various systems.)  The default in this
+ case, obviously, is not to include support for multi-threading (but
+ you can still use "no-threads" to suppress an annoying warning message
+ from the Configure script.)
+
 
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 The orignal Unix build instructions from SSLeay follow.