Add OPENBLAS_L2_SIZE and improve formatting

Author: martin-frbg

docs/runtime_variables.md

@@ -2,18 +2,20 @@
 
 OpenBLAS checks the following environment variables on startup:
 
-* **OPENBLAS_NUM_THREADS=**   the number of threads to use (for non OpenMP-builds of OpenBLAS)
+* **OPENBLAS_NUM_THREADS=**   the number of threads to use (for non-OpenMP-builds of OpenBLAS)
 * **OMP_NUM_THREADS=**        the number of threads to use (for OpenMP builds - note that setting this may also affect any other OpenMP code)
 * **OPENBLAS_DEFAULT_NUM_THREADS=**   the number of threads to use, irrespective if OpenBLAS was built for OpenMP or pthreads
 
 * **OPENBLAS_MAIN_FREE=1**"   this can be used to disable automatic assignment of cpu affinity in OpenBLAS builds that have it enabled by default
 * **OPENBLAS_THREAD_TIMEOUT=**  this can be used to define the length of time that idle threads should wait before exiting
 * **OMP_ADAPTIVE=1**      this can be used in OpenMP builds to actually remove any surplus threads when the number of threads is decreased
-* 
+
+
 DYNAMIC_ARCH builds also accept the following:
 * **OPENBLAS_VERBOSE=**       set this to "1" to enable a warning when there is no exact match for the detected cpu in the library
-*                             set this to "2" to make OpenBLAS print the name of the cpu target it autodetected
+                              set this to "2" to make OpenBLAS print the name of the cpu target it autodetected
 * **OPENBLAS_CORETYPE=**      set this to one of the supported target names to override autodetection, e.g. OPENBLAS_CORETYPE=HASWELL
+* **OPENBLAS_L2_SIZE=**       set this to override the autodetected size of the L2 cache where it is not reported correctly (in virtual environments)