Add comments to README about compiler and library dependencies.

git-svn-id: svn://svn.berlios.de/openocd/trunk@2441 b42882b7-edfa-0310-969c-e2dbd0fdcd60

README

@@ -128,7 +128,14 @@ those looking for a quick-install
 OpenOCD Dependencies
 --------------------
 
-You will need to install the appropriate driver files, if you want to
+Presently, GCC is required to build OpenOCD.  The developers have begun
+to enforce strict code warnings (-Wall, -Werror, -Wextra, and more) and
+use C99-specific features: inline functions, named initializers, mixing
+declarations with code, and other tricks.  While it may be possible to
+use other compilers, they must be somewhat modern and could require
+extending support to conditionally remove GCC-specific extensions.
+
+Also, you need to install the appropriate driver files, if you want to
 build support for a USB or FTDI-based interface:
 
 - ft2232, jlink, rlink, vsllink, usbprog, arm-jtag-ew:
@@ -139,6 +146,9 @@ build support for a USB or FTDI-based interface:
     or the Amontec version (from @uref{http://www.amontec.com}), for
     easier support of JTAGkey's vendor and product IDs.
 
+Many Linux distributions provide these packages through their automated
+installation and update mechanisms.
+
 Compiling OpenOCD
 -----------------