just by skipping alpha*matrix multiplication when alpha == 1.0.

All tests succeed (with blas.ldflags empty) for:
* test_abstract_conv.py in theano/tensor/nnet/tests/
* test_blas.py and test_blas_scipy.py in theano/tensor/tests/

I have modified theano/tensor/tests/test_blas_c.py
to skip all tests that involves either gemv or ger functions.
* Before the modifications, this file executed 44 tests and 34 were skipped.
* After  the modifications, this file executes 44 tests and 29 are skipped.

# $ theano-cache purge && THEANO_FLAGS=blas.ldflags= nosetests --verbose theano/tensor/tests/test_blas_c.py

PS: I also tried to execute test_corr.py in
theano/tensor/nnet/tests/test_corr.py after removing ldflags checking,
but I get many errors in many of the tests (theano outputs not matches ref outputs).
So for the moment I have let this file and I will continue investigations tomorrow.

Recall: code is tested with:

$ theano-cache purge && THEANO_FLAGS=blas.ldflags= nosetests theano/tensor/nnet/tests/test_abstract_conv.py:TestCorrConv2d

NB:
1) dgemm_ is never called in these tests. Only sgemm_ is called.
2) All LDA,LDB,LDC are always in the set {M;N;K} during these tests.

I added an implementation of C-functions "sgemm_" and "dgemm_" that call Numpy C-API functions to perform matrix product when BLAS is explicitely disabled (with theano flag "blas.ldflags" set to empty).

This can be tested with:
THEANO_FLAGS=blas.ldflags= nosetests theano/tensor/nnet/tests/test_abstract_conv.py:TestCorrConv2d

Somewhat smaller/faster 3d convolution tests

A few small update.

Scan with Checkpoints (part 2)

Fix a change to gpuarray conv from gh-5069. dnn conv wasn't working a…

32bit

Cudnn RNN bindings.

Make device=gpu with floatX=float16 raise an error (cause many user q…

Make device=gpu with floatX=float16 raise an error (cause many user questions and this should never be used). if floatX=float64, raise an error.

fix tests in mode=FAST_COMPILE

GpuCorrMM and GpuCorr3dMM in new backend