build: remove workarounds for gcc <= 4.4

Now that V8 requires a compiler with decent C++11 support, there is no
reason to keep supporting old versions of gcc.  Remove workarounds for
bugs in gcc 4.4 and older.

This coincidentally makes it easier to build with clang 3.3 + address
sanitizer because clang no longer chokes on the `-fno-tree-vrp` switch.

PR-URL: node-forward/node#24
Reviewed-By: Fedor Indutny <fedor@indutny.com>

common.gypi

@@ -84,12 +84,6 @@
             # pull in V8's postmortem metadata
             'ldflags': [ '-Wl,-z,allextract' ]
           }],
-          ['clang == 0 and gcc_version >= 40', {
-            'cflags': [ '-fno-tree-vrp' ],  # Work around compiler bug.
-          }],
-          ['clang == 0 and gcc_version <= 44', {
-            'cflags': [ '-fno-tree-sink' ],  # Work around compiler bug.
-          }],
           ['OS!="mac" and OS!="win"', {
             'cflags': [ '-fno-omit-frame-pointer' ],
           }],