configure: add --enable-static option

Fixes issue #62.

Change-Id: I0567cf7897c0942666c19b3231c8c3b8e9c3e7cc

configure

@@ -40,6 +40,7 @@ Advanced options:
   ${toggle_error_concealment}     enable this option to get a decoder which is able to conceal losses
   ${toggle_runtime_cpu_detect}    runtime cpu detection
   ${toggle_shared}                shared library support
+  ${toggle_static}                static library support
   ${toggle_small}                 favor smaller size over speed
   ${toggle_postproc_visualizer}   macro block / block level visualizers
 
@@ -153,6 +154,7 @@ enabled doxygen && php -v >/dev/null 2>&1 && enable install_docs
 enable install_bins
 enable install_libs
 
+enable static
 enable optimizations
 enable fast_unaligned #allow unaligned accesses, if supported by hw
 enable md5
@@ -252,6 +254,7 @@ CONFIG_LIST="
     realtime_only
     error_concealment
     shared
+    static
     small
     postproc_visualizer
     os_support
@@ -293,6 +296,7 @@ CMDLINE_SELECT="
     realtime_only
     error_concealment
     shared
+    static
     small
     postproc_visualizer
 "